People love groups, plain and simple. There is something innately fascinating about grouping together people, places, or things in order to express a point or frame an argument. In baseball especially, representative groupings are important given the very large quantity of available information.

One group mentioned frequently around these parts and others is what I like to call “The ‘90s Nine,” a nonet of pitchers that defined their craft in this most recent era, peaking for the most part in the 1990s. The cast members: Roger Clemens, Greg Maddux, Randy Johnson, Pedro Martinez, Tom Glavine, Mike Mussina, John Smoltz, Curt Schilling, and Kevin Brown. Clearly, some of those pitchers are superior to others, but if someone were to ask me to rattle off the names of pitchers without whom the story of pitching from say 1989-2003 could not be told, these nine would instantly shoot to the top of the list. But my goal today is not really to discuss the merits of this specific group. Instead, I would like to carve out a list of who would define the most recent decade or era, a fairly tough exercise given that baseball memories are developed in a much more fluid fashion.

To begin, I would be remiss to neglect to mention that, no, I do not consider everyone in the aforementioned group to be equal. There is a fairly evident gap between the likes of Clemens, Maddux, Johnson, and Martinez and the remaining quintet. That being said, those nine pitchers were the best of their era, and while Kevin Brown may have ended his career in quite the unceremonious fashion, he was still dynamite for a long, long time and definitely worthy of being included. Similarly, the group that will be discussed today can also be broken up into separate bins.

What proved interesting, though, when compiling this list was the gap in talent between the '90s Nine and pitchers of this era. We certainly bore witness to some great pitchers over the last decade, but nobody is realistically close to Maddux, Johnson, Martinez or Clemens. That group boasted four of the top pitchers in the history of the game, all of whom happened to peak at around the same time, while remaining very effective after that peak ended.

The new group has plenty of talent, but not like the last one, and it does not really stake claim to pitchers with comparable periods of effectiveness. For instance, one could argue that pitchers like Mark Mulder and Matt Morris were worthy of inclusion at the beginning of the decade, a silly thought in retrospect as their effectiveness was shorter-lived. In other words, this era seemed to have a greater number of guys who were very good for a couple of years but who then gave way to a newer crop of very good pitchers, making it tough to arrive at any type of a consensus.

The mere fact that I felt compelled to e-mail several of my BP colleagues to brainstorm tells me that this was a much tougher era to define from a pitching standpoint. The shorter spurts of dominance also meant that certain pitchers who really came into their own at the tail-end of the decade were worthy of inclusion—after all, it isn’t as if they weren’t the best of the best in their run, and they should not exactly be penalized for dominance at the end of an arbitrary span.

As that brainstorming began, it became abundantly clear that there were two types of pitchers to include: those who have been very good for a very long time, and those whose peaks were great even if they haven’t been at it for all that long. Pitchers who came into their own this year or have supreme ace-dom in their future are beyond the scope of this article. Josh Johnson is a stud; Ubaldo Jimenez is young and has looked unhittable at times; Stephen Strasburg looks to be a legitimate ace in the making; Justin Verlander and Felix Hernandez may well continue to develop into perennial award candidates; and there are few pitchers I’d rather have on the mound right now than Adam Wainwright. However, none of these pitchers are included, primarily in that they are more suited to headline future lists than ones defining this past decade.

With that disclaimer out of the way, pitcher selection did not rely on some specific process. I didn’t simply examine WARP3 leaders or sort the pitchers by their ERA or SNWP. Instead, I used a variety of tools, including the statistics mentioned above and others, as well as my own feel for the game, in order to determine which pitchers made the most impact. Without further ado, let me present to you the ‘00s Ten, the 10 hurlers who define the last decade or so of pitching:

Group One: Very Good for a Long Time

Roy Halladay
Probably the best pitcher in the sport now and over the last several seasons, since turning the corner in 2002 and becoming the Doc we know and admire today, Halladay has a 3.04 ERA and 1.12 WHIP in 1,888 1/3 innings pitched. His 60.5 SNLVAR ranks as the highest in the sport over that span, and his .613 SNWP just barely ranks second to Johan Santana. His 3.04 ERA also ranks second in the game in that span, as do his WHIP and SIERA marks; with a 1,500 IP minimum, only Santana ranks ahead in these categories. Factor in how he has seemingly been improving over the last few seasons—a 2.62 ERA and 1.07 WHIP with 26 complete games and nine shutouts since 2008—and has been a dominant force throughout the entire decade, any list without Halladay at its top is in need of some serious scrutiny.

CC Sabathia
There is a reason many consider Sabathia to be the last true shot at a 300-win pitcher: he is filthy and has been since bursting onto the scene as a 20-year-old in 2001. Sabathia has never logged fewer than 180 innings in a season and averaged 229 over his last four full seasons. At just 29 years old, Sabathia is still in the midst of his peak, and put up stellar numbers over the last year and a half in spite of playing in baseball’s toughest division. Since 2006, his 1,074 2/3 innings ranks second only to Halladay, while his 3.12 ERA ranks sixth. When normalized for league differences, the rate looks even better.

Additionally, his .598 SNWP ranks fifth over the last four and a half seasons, while his 31.31 SNLVAR ranks third to just Halladay and Santana. Sabathia helped lead the Yankees to a World Series championship last season, and it wouldn’t shock me in the least to see him win at least one more in pinstripes. How he ages will be a mystery until we see it happen, but it does not, in any way, detract from what he has done over these past 10 years.

Roy Oswalt
Oswalt has suffered from what I like to call Abreu-Syndrome, in that he was underrated during his peak, and by the time the vast majority began to take notice, his underlying skills started to erode. That happens when you become the de facto third starter to the Clemens and Andy Pettitte tandem. From 2002-07, Oswalt produced a 3.11 ERA that ranked fourth to Santana, Smoltz, and Martinez. His .586 SNWP also ranked sixth in that span to the aforementioned trio, Clemens, and Halladay.

Oswalt isn’t a potential Hall of Famer like Halladay and Sabathia, but he was hands down one of the most effective pitchers of the decade, mixing mid-90s heat with a devastating curveball in the low 70s. He appears to be on the decline as of late, but a declining Oswalt is still a better pitcher than many others in their peak.

Tim Hudson
For the first half of the decade, Hudson was intertwined with Barry Zito and Mark Mulder, forming a “big three” that some thought could rival Maddux, Glavine, and Smoltz. However silly that sentiment was, the Oakland trio was truly the closest thing baseball had to another dominant threesome, and Hudson led the group. While Zito won an AL Cy Young Award and Mulder came close, Hudson was the ace of the staff, a fact many did not realize until he had been traded to the Braves. In six seasons with the Athletics from 1999-2004, Hudson produced a 3.30 ERA in 183 starts, keeping the ball on the ground and proving effective in terms of limiting walks.

Over that six-year span, Hudson’s 38.93 SNLVAR ranks fourth to Martinez, Johnson and Schilling, and he may have even overtaken Schilling given that his 1999 campaign was not a full season. Additionally, his SNWP over those six seasons was .595, which ranked fifth to the three Hall of Famers just mentioned plus Brown. As a member of the Braves, he has a 3.55 ERA in 150 games (149 starts), and while his strikeouts have decreased a bit, his propensity for limiting walks and inducing grounders is as good as ever. Since 2005, Hudson has 28.24 SNLVAR, which ranks 11th, and is made all the more remarkable by the fact that his 2008 and 2009 seasons essentially combine for one full season—meaning he missed the equivalent of a full season to injury.

With that season back it is more likely than not that his mark would place him in the top five or six. No matter how one chooses to slice up the decade, Huddy was one of the best, and if his 2010 season is any indication, he still is one of the best.

Johan Santana
I remember watching a Twins game back in 2003 in which Johan came in as a reliever. I wasn’t a stathead yet, nor was I a scout or someone with any knowledge of where Santana ranked on prospect lists, but I remember seeing his funky windup and effective results and immediately telling friends I thought he was going to be really good. Over the next three years Santana would prove me quite prescient. From 2004-06, he won two AL Cy Young Awards, should have won a third if not for people falling in love with Bartolo Colon’s 20-plus wins, and put up the following numbers: 101 GS, 2.75 ERA, 146 BB, 748 K. He struck out 28 percent of the batters he faced while walking 5 percent. His WHIP fell under the 1.00 threshold and he averaged 231 innings a season.

Since then his career has been interesting, as the ERA marks have been quite stellar, but the underlying numbers have all declined. It is tough to poke holes in the game of someone for whom a 3.20 ERA represents a decline, but Santana is in the midst of his worst peripherally oriented season, with a drastically reduced strikeout rate. Regardless, his peak of 2004-06 was so incredibly dominant that he belongs on this list, in this group, on the merits of those three years alone. But when factoring in his numbers as a starter at the end of the 2003 season and his effectiveness since 2006, it isn’t a reach at all to label him one of the top five pitchers of the era.

Group Two: Great Peak, Success Not as Lengthy

Chris Carpenter
Once upon a time, Carpenter and Halladay were thought of as the bright future of Blue Jays pitching. Obviously, the best-laid plans did not come to fruition, but Carpenter resurfaced with the Cardinals following a couple of lengthy injuries and lived up to prior expectations. Since joining the Cardinals in 2004, Carpenter has a 2.91 ERA in 150 games (149 starts), with a 20.2 percent strikeout rate and a low 5.4 percent walk rate. He won the Cy Young Award in 2005, very easily could have won it in 2006, and came within a vote or two of winning it again in 2009, a year in which he tied the wild-card era record for fewest home runs allowed. He has been overshadowed recently by Wainwright on the Cardinals' staff, but Carpenter was certainly one of the best of this decade, and if it were not some recent injuries he might have even belonged in the first group.

Cliff Lee
There are solid arguments on both sides of the coin for whether or not Lee deserves to be included. On one hand, he didn’t really become that great until the latter part of the decade, even being famously left off of the Indians’ 2007 playoff roster. Then again, he has been so incredibly dominant from 2008-10 that fans and analysts now tend to lump him in with Halladay when describing “true aces.” For instance, two or three years ago it might have been common to hear someone say, “Well, Pitcher X is good, but he’s not a Halladay.” Nowadays, the line has been modified: “Well, Pitcher X is good, but he’s not Halladay or Lee.”

Anyone who has been so effective over a three-year span so as to be considered one of the two best pitchers in the sport has to be included here, even if that span came as the decade wound to a close. Since 2008, Lee has made 83 starts while producing a 2.83 ERA, striking out 469 in 602 innings. He has also issued just 86 walks to the 2,432 batters faced over that span, a rate of 3.5 percent. He won the AL Cy Young Award in 2008 with an incredible season and barring something strange—like him not picking up another win over the next two months—voters will be hard-pressed to vote for anyone else this year. Sandwiched between those years was one in which he helped guide the Phillies to their second consecutive World Series appearance. The man can pitch.

Tim Lincecum
Just like the pitcher discussed above, Lincecum was fashionably late to the party, but has certainly made his presence felt after arriving. This will mark only his third full season in the big leagues, but since joining the fray in the middle of the 2007 season, very few pitchers have put up better numbers than The Freak. His 25.16 SNLVAR since 2007 ranks third to Halladay and Sabathia, and his .611 SNWP ranks second only to Halladay. Lincecum won the NL Cy Young Award in both 2008 and 2009, and is putting together another stellar campaign, even though his 3.10 ERA looks relatively high given the performances of several other stars of Year of the Pitcher, a 2010 production. Either way, several years from now, we are going to look back at the end of this decade and remember the emergence of Lincecum as a pitching force to be reckoned with, so he belongs.

Jake Peavy
Yes, Peavy pitched in Petco Park for most of his career, and no, he has not been a dominant force since joining the White Sox last summer, but look past the most recent results and you will find one of the best pitchers of the decade. From 2004-09, he put up a 2.99 ERA in 1,070 1/3 innings, striking out 26 percent of the opposition while walking just 7 percent. In that span, his 36.92 SNLVAR ranks fourth to Santana, Halladay, and Oswalt, and his .605 SNWP ranks third to just Johan and Halladay. Add in his Cy Young Award and he’s a lock for this list.

Josh Beckett
Metaphorically speaking, I tossed and turned over Beckett’s inclusion. It is hard to argue with the facts that he was certainly dominant and became one of the best playoff pitchers in baseball history this decade, but something didn’t fit for me initially. Maybe it was expectations that weren’t realized until the 2003 postseason and then a poor 2006 season with the Red Sox. Who knows? But in any event, I realized that no list would accurately describe the pitchers of the decade without Beckett. He might not have had the peak of Santana, Lee, or Lincecum, and he might not have been very good for as long as Sabathia, Halladay, Oswalt, and Hudson, but he has put up solid numbers in the toughest division for a good amount of time, and has excelled in the playoffs. If for no other reasons than those he belongs, though it wasn’t a slam-dunk decision.

Other Considerations
There were a few names I considered but who were eventually cut before this article went to press. The first was Pettitte, who has put together a very good career and, depending how long he pitches, he might end up being even the last 265-270 game winner. Still, he was more good than great, was never dominant, and while he may be one of my personal favorite pitchers of all time, his name simply looked odd when listed alongside the nine pitchers discussed above.

Then there were a couple of pitchers who showed up in league leaders in various statistical categories, but who I do not feel belong. For instance, Mark Buehrle and Carlos Zambrano routinely surfaced in the top 10 or 15 in rates and raw tallies, but I would argue that both were merely good for a lengthy period of time as opposed to great for an extended period of time like our first tier above, or above great for a shorter period of time like those in our second tier. After those two, we had Dan Haren and John Lackey, who were both effective over the course of the decade but who did not give me that feeling that they will be remembered as era-defining hurlers.

So what do you think? Is there anyone who should belong that isn’t there? If so, please provide your mindset, as this was not an easy list to compile and I would love to hear what others have to say. There is no right or wrong here either, just fun and opinions.