1. Jon Niese
Now 25, Niese is nearing the age where he needs to make good on his promise, or otherwise be labeled a fourth starter for good. Niese, a big lefty with the stuff to pitch inside to righties and get ground balls, improved on his peripherals in 2011 but saw his earned run average worsen. Assuming Niese’s abdominal strain doesn’t become an issue again, this could be the season he posts an earned run average better than the league average. —R.J. Anderson

​2. Brandon Belt
Brandon Belt's minor-league credentials speak for themselves. In 825 plate appearances, his line stands at a ridiculous .343/.457/.596. He was highly regarded coming into 2011, but played for a manager who hasn't been comfortable with rookie hitters since being burned by George Arias and Ruben Rivera many moons ago. At age 24, Belt might not have star potential, but .280/.370/.480 is within reach, which is something most guys in the Giants' lineup cannot claim. —Geoff Young

3. Ryan Lavarnway
Much like Shaquille O'Neal, who you will recall claimed to have won at every level "except college and the pros," Ryan Lavarnway has hit at every level. Except, he actually has. Since starting his pro career in Low-A, Lavarnway hasn't posted an OPS below 869 at any stop on the minor-league ladder. At 23, he'll probably start the year in Triple-A, but he posted an OPS of 1.002 in 264 PAs in Pawtucket last season so barring injury, there are significant at-bats in Boston for him this season. His good plate discipline and right-handed power will push him into the Red Sox' lineup, and by the end of the season he'll be a Rookie of the Year candidate. —Matthew Kory

4. Fernando Martinez
Fernando Martinez has averaged fewer than 300 plate appearances per season since coming to the U.S. as the Mets' $1.3 million bonus baby in July 2005. Despite leg injuries that have rendered him a below-average runner, Martinez still shows flashes of the ability that made him the Mets' top hitting prospect from 2008-2010. In January, after spending parts of the last three years in Triple-A, Martinez signed with Houston as a six-year minor-league free agent. I believe the Astros will find a way to keep Martinez healthy, and that the 23-year-old post-hype sleeper will handily outplay his competitors (Brian Bogusevic and Jack Cust) to earn regular playing time in right field. —Bradley Ankrom

5. Colby Rasmus
There are a number of factors that could be converging for Rasmus this season. He’s the unquestioned starter at a premium position on a rising team that actually wants him. He's coming off an injury that wrecked his 2011 numbers and has lots to prove. He’s 25 years old, turning 26 in August, which to me is a great age for a center fielder. I think he’s going to not only recover the numbers he had in his last full season in St. Louis, but in fact blow by them. It’ll help if he can walk more than once every 28 plate appearances, which is what he did after being traded to Toronto. —Bradford Doolittle

6. Dexter Fowler
The 26-year-old Fowler might seem a curious breakout choice, given that he is coming off a 4.8 WARP season. But Fowler compiled the bulk of his 2011 value through plate discipline and defense which, while valuable, are only two components of a much deeper skill set. The Rockies demoted Fowler after a DL stint in June because, at the time, he was batting a lowly .238/.340/.352. Fowler's walk rate was certainly impressive, but he had notched just 18 extra-base hits (0 home runs) in 247 plate appearances, which was not enough to warrant staying in Jim Tracy's starting lineup.

That all changed when he was brought back from Triple-A after the All-Star break. Fowler suddenly began tapping into his power, producing five homers—among 37 total extra-base hits—in 316 plate appearances from July 15 through the end of the season. His triple-slash after the promotion was an excellent .288/.381/.498, and while both the batting average and slugging percentage are likely to regress, that's more in line with Fowler's ability than the 692 OPS his posted between April and early June.  
If Fowler can play like he did last summer over the course of a full season, he has a chance to blossom into one of the best players in the National League—both in a real-life and a fantasy baseball sense. The Fowler we saw last summer is the player he was expected to become when Kevin Goldstein ranked him as a top-12 prospect heading into the 2009 season. Fowler may have developed more slowly than expected, but he is now ready to stand beside Matt Kemp among the senior circuit's elite. —Daniel Rathman
7. Wilson Ramos 
My choice for this week’s Lineup Card is one that will make Twins fans cringe and Nationals fans stay optimistic about their team’s ability to make a playoff run sooner rather than later. Wilson Ramos only ended up being traded to Washington because Joe Mauer blocked him behind the dish in Minnesota. Last year, as a 23-year-old rookie, Ramos hit .267/.334/.445 (.332 wOBA) in 113 games. Those are impressive numbers for any rookie, much less one at the most demanding defensive position in the sport.

Ramos will not only be asked to continue to improve offensively this season, but also defensively, as Edwin Jackson and Gio Gonzalez join the rotation and Stephen Strasburg returns to it. He has shown to be up to the task defensively, but his relationship with the arms in the 2012 rotation will be crucial to the team’s hopes to compete in the loaded NL East. While PECOTA expects a slight dip for Ramos at the plate, it is not beyond reason to expect him to improve on his stellar rookie campaign. As long as he doesn’t get overworked defensively at catcher, his offensive numbers should continue to shine at the bottom of a lineup filled with young talent. It rides on a lot more than just his contributions, but if Ramos is able to continue his success both at and behind the dish, the Nationals could surprise their way into contention. —Sam Tydings

8. Rick Porcello
At age 23, Detroit Tigers RHP Rick Porcello has already started 89 big-league games. He has also won 14 games twice, started a one-game playoff, and seen his strikeout total rise to over 100 (104 in 2011), all the while increasing his WARP from 0.1 (at age 20) to 1.1. To expect more from Porcello is to expect him to begin to live up to the potential that made the Tigers draft him with the 27th overall pick in the 2007 draft (he carried a top-10 projection but fell due to signability), and give him a four-year major-league deal worth $7.285 million plus club options for 2011-2012. 

Porcello has had those 14-win seasons through sheer talent, and he'll break out in 2012, harnessing that raw talent into a veteran presence. Look for Porcello to win 17-20 games, bring his ERA below 4.00, and increase his WARP. —Adam Tower

9. Mat Latos
There’s perception and then there’s the reality. The “perception” is that Mat Latos, dogged by shoulder issues and maturity questions struggled through an unproductive 2011 season, leading the Padres to deal him to the Reds for a haul of prospects and a former All-Star in Edinson Volquez

The reality? In his “injury-plagued” season, Latos threw 194 innings, posting an ERA of 3.28 and fanning a man an inning over the season’s final five months. A prototypical power pitcher, Latos turned 24 this past December. He’s posted a nearly identical home-run rate on the road as he did at cavernous Petco Park, and has a 3-to-1 strikeout-to-walk ratio. 
In an interview Tuesday on MLB Network Radio, new Reds pitching coach Bryan Price said he believes Latos has the tools to take that next step. 
“I think a lot of it has to do with setting your goal to be that guy. I think he’s willing to do that work.  I think there’s a certain amount of development through maturity, as far as… logging seasons and being around people to learn from. I think he has the ability to do that, and the willingness as well.”
Latos has the stuff and experience to become a true number-one starter, but baseball kinds needs him to become a star for another reason: He’s a character. Latos has been willing to tweak arch-rivals and their fans, and like “Nuke” Laloosh and his fungal shower shoes, his personality becomes more interesting the more he wins. Baseball could certainly use more of that. —Mike Ferrin
In my early teenage years, I did some writing for a couple of High-A ballclubs in Southern California: the Lake Elsinore Storm (still a Padres affiliate) and the Inland Empire 66ers (then a Seattle Mariners affiliate). One of my first interviews was with Bryan LaHair, and when he hit a game-winning homer later that evening, my prospect crush was born. I swore that he was going to make the majors. 
As Steve Goldman can attest, I've remained vigilant in that conviction, despite scouts and teams branding LaHair as an organizational soldier. And really, his stats haven't been all that eye-popping. Scouts started paying more attention to the first baseman in 2010, when he hit .308/.385/.557 at Triple-A Iowa and showed increased patience at the dish. LaHair kicked up his slugging in 2011, knocking 38 homers and 38 doubles, and beefed up his OBP to .405, helping him to a 1.070 OPS in 129 games. The Cubs gave him a cup of coffee at the end of the year, and he held his own with a .288/.377/.508 performance in 20 games. 
Carlos Pena skipped town over the winter to soak up some Rays, leaving the first-base job to LaHair… until the Cubs traded for Anthony Rizzo. But Rizzo still needs some seasoning in Triple-A, meaning that LaHair is clear for takeoff in April. I don't think he's going to put up huge numbers—I can be realistic when I have to be—but I do think he'll be able to hold his own in extended playing time. For a guy who has played minor-league journeyman for eight years, I think that's good enough to be considered a breakout. —Stephani Bee
If you've forgotten how highly touted Justin Smoak was as a prospect, remember that the Mariners opted to trade for him—and not Jesus Montero—for Cliff Lee. Overall, his line was not good last season, but this is tempered when one realize he was battling thumb injuries and dealing with the death of his father. Smoak posted good numbers in the minors despite 174 games played at all minor league levels combined since 2008, but now entering his age-25 season, and no longer unfamiliar with major-league life, if Smoak can stay healthy, he should be a prime breakout candidate. —Rebecca Glass
The overall number two pick in the 2007 draft, Moustakas came into last year as the top prospect in the best system in baseball, and seventh on Kevin Goldstein's Top 101 Prospects list. He made his major-league debut in June, three months shy of his 23rd birthday, but his overall numbers were nothing to write home about: a .263/.309/.367 line with five homers and 22 walks in 365 plate appearances, for a .251 True Average.

A closer look at those numbers suggests plenty of reason for optimism. The Moose was hitting an anemic .182/.237/.227 through his first 53 games and 217 plate appearances when he began a 15-game hitting streak that included eight multi-hit games. He hit a searing .379/.412/.564 over his final 148 PA, and while much of that came against second-division clubs, we are talking about a player in the AL Central, where four of the five teams (besides the Royals) finished below .500. He's not going to match those late-season numbers, and PECOTA isn't exactly gushing with optimism (.267/.304/.433 for a .260 TAv), but I'm picking him to be a player who breaks out in 2012. —Jay Jaffe

You might not guess based on his mediocre strikeout numbers—he posted just a 6.8 K/9 at Double-A in 2011—but Henderson Alvarez actually throws the ball around 93 mph and doesn’t struggle to crank it up to 97 or 98, reportedly even touching 100 mph on the radar gun on occasion. Just looking at the stats you might guess that he’s a soft osser who gets by on command, but he has the potential to be so much more. Of course, that plus command doesn’t hurt one bit, nor does his excellent ground ball-inducing ability. Even without a ton of whiffs he should be good, but Alvarez could really be something special if his stuff ever translates into strikeouts. His ability to do so will be limited a bit since his fastball is closer to a sinker than it is to a rising four-seamer, but Alvarez is an intriguing guy that many may overlook based on his numbers (though probably fewer now that Jason Collette and I have both touted him as a sleeper). PECOTA is pessimistic because of his lack of upper-level experience, but I believe that he's able to at least hold his own right now. —Derek Carty
Yonder Alonso seemingly didn't get a fair shake when he was traded from the Reds to the Padres over the winter; the 24-year-old first baseman will go from one of the best hitting environments in baseball in Great American Ball Park to the worst in Petco Park. Yet it really doesn't matter where a player plays his home games if he doesn't get a chance to play. It had become clear Alonso wasn't going to get an opportunity in Cincinnati with Joey Votto entrenched at first and Reds owner Vince Castellini reportedly ready to pull out all the stops to keep him from becoming a free agent. Alonso doesn't hit with the same power as Votto; his career high for home runs in his three full professional seasons is 17. However, Alonso is a gap hitter, and that style should play very well in Petco Park's spacious alleys. If Padres manager Bud Black writes his name on the lineup card every day—and he should, with all due respect to Jesus Guzman—Alonso has the talent to do the rest. —John Perrotto