With the end of the decade upon us, the task of identifying the best and worst singleseason teams over the course of the past 10 years isn’t a difficult one, even if we move beyond simple wonloss record. While we can debate the relative merits of teams’ excellence at the plate, on the mound, or in the field according to a variety of metrics, at the end of the day, the elementary relationship between runs scored, runs allowed and winning percentageso basic that Bill James likened it to the algebraic Pythagorean Theorem more than a quarter century agoremains the best standard by which to judge teams. Even with the various enhancements we at BP add to the basic Pythagorean framework, adjusting for park, league, and quality of opposition, the inescapable conclusion is that the 2001 Mariners were the best team of the decade, and the 2003 Tigers the worst. In fact, the standards those two teams set carry the day over an even longer timeframe.
Clearing the nuts and bolts before we dive into this candy dish, recall that instead of simply relying upon the Jamescreated Pythagorean Equation (Winning Percentage = Runs Scored^2 /( Runs Scored^2 + Runs Allowed^2), we publish three related derivations which are based upon a modification of that formula called Pythagenpat, where the power of the exponent varies with the scoring level:

Firstorder winning percentage uses actual runs scored and allowed.

Secondorder winning percentage uses equivalent runs scored and allowed, based on run elements (hits, walks, total bases, stolen bases, etc.) and the scoring environment (park and league adjustments).

Thirdorder winning percentage adjusts for the quality of the opponent’s hitting and pitching via opposing hitter EqA (OppHEqA) and opposing pitcher EqA (OppPEqA).
Over the past five years, I’ve used the the average of a team’s actual and Pythagenpat winning percentagesknown as the Hit List Factorto run the Prospectus Hit List, our weekly power rankings (see here for more). While HLF doesn’t adjust to account for league difficulty, it does provide a useful benchmark for for measuring relative dominance. When we compare HLFs across the entire decade, the 2001 Mariners are the runaway leaders:
Year Team WL Win% RDif* HLF 2001 Mariners 11646 .716 300 .687 2001 Athletics 10260 .630 239 .642 2004 Cardinals 10557 .648 196 .625 2007 Red Sox 9666 .593 210 .624 2002 Angels 9963 .611 207 .623 *: Run differential
The Mariners tied the 1906 Cubs for the majorleague record for wins, though it took them 162 games to accomplish what the Cubs did in a preexpansion schedule of 154 games. The M’s also broke the 1998 Yankees‘ freshlyminted record for the most wins by a team over the course of a 162game season (114). Even without Alex Rodriguez (departed via free agency over the previous winter), Ken Griffey Jr. (traded in February 2000), or Jay Buhner (limited by injuries to just 19 games), Seattle’s offense led the league in scoring at 5.7 runs per game. Newcomer Ichiro Suzuki rapped 242 hits, hit a leaguebest .350, and won both Rookie of the Year and MVP honors, Bret Boone bashed 37 homers and collected 206 hits, and Edgar Martinez, John Olerud, and Mike Cameron all had strong years as well. Meanwhile their pitching staff, which had seen Randy Johnson traded just two seasons earlier, allowed the league’s fewest runs per game at 3.9, as Freddy Garcia, Aaron Sele, and Jamie Moyer all tossed more than 200 innings with ERAs of 3.60 or lower. Manager Lou Piniella simply had little to throw a tantrum about.
Those Mariners outscored opponents by 300 runs, nine less than the 1998 Yanks but 61 more than any team in this decade, with their own divisionmates, the 2001 A’s in secondthat was the team with Jason Giambi, Miguel Tejada, and Eric Chavez in their primes, along with the big three of Tim Hudson, Mark Mulder, and Barry Zito. The Mariners’ overall record was well ahead of their Pythagenpatbased winning percentages thanks in part to a leagueleading WXRL total, but even the most conservative projection of their recordvia their .675 thirdorder Pythagenpatwas well ahead of the pack. In fact, the Mariners’ Hit List Factor was higher than any other team since World War II, with only the 1998 Yanks (.682), 1954 Indians (.677), 1969 Orioles (.677) and 1953 Yankees (.661), cracking the alltime top 25. Other than teams from the first decade of the 20^{th} century, only two megafamous Yankees clubs, the 1939 model (.713) and the 1927 club (.693), top those Mariners.
The irony, of course, is that those Mariners didn’t seal the deal with a World Series win, instead falling to the Yankees in the AL Championship Series in five games. Anything can happen in a short series, of course, and it’s worth noting that neither the second or thirdranked teams on this list won the World Series either. Still, by the standards of the 162game long haul, the 2001 Mariners tower over the decade’s field.
Just the same, the 2003 Tigers cower under it:
Year Team WL Win% RDif HLF 2003 Tigers 43119 .265 337 .292 2002 Tigers 55106 .342 289 .326 2004 Diamondbacks 51111 .315 284 .327 2002 Devil Rays 55106 .342 245 .357 2005 Royals 56106 .346 234 .360
The franchise of Cobb, Cochrane, and Kaline had already fallen upon hard times coming into 2003, having suffered nine consecutive losing seasons, the worst of which came via their immediate predecessors. The 2003 club, helmed by longtime Tiger shortstop and rookie skipper Alan Trammell, was something else entirely. Only by winning five of their final six games did they avoid the legendarily awful 1962 Mets‘ 40win, 120loss standard of futility. Their offense finished last in the league in scoring at 3.6 runs per game, with only three regularsDmitri Young, Carlos Pena, and Eric Munsonmanaging even a leagueaverage .260 EqA. Other regulars like Brandon Inge, Ramon Santiago, and Shane Halter finished at .211 or lower, well into replacementlevel territory.
Meanwhile, the Tigers’ pitching was secondtolast in the league in runs allowed, with Mike Maroth becoming the first pitcher since Brian Kingman in 1980 to lose 20 games, and rookie Jeremy Bonderman (619 with a 5.56 ERA) missing thanks only to a September spent in the bullpen. Nate Cornejo was the only starter with an ERA better than Bonderman’s; he finished at 4.67, still worse than league average. Their bullpen ranked last in the league in WXRL, which helped the team’s actual record wind up five or six wins below even their miserable Pythagenpat projections.
Those Tigers actually outdid the original Mets in a few ways: they were outscored by 337 runs, six more than the Mets, their Hit List Factor was four points worse, and they lacked expansion as an excuse. No other postwar team is even close to those two, and aside from a few wartorn Phillies clubs, the only postDeadball Era team to surpass them in futility was the 1932 Red Sox (43111, .291 HLF). The postwar bottom five would consist of those Tigers and the ’62 Mets, plus the 1954 Philadelphia A’s (.305), 1952 Pirates (.307), and 1969 Padres (another expansion club, .313).
So while recognizing the decade’s best and worst teams’ didn’t yield any surprises on either score, as we look back across those 10 years, it’s at least worth remembering that the extremes they achieved were history in the makingfor better and for worse.
A version of this story originally appeared on ESPN Insider .