Six weeks into the baseball season, 10 teams have been outscored by 20 runs or more, and, not surprisingly, nine of them sport losing records. The lone exception, Arizona, is 23-18 despite allowing 196 runs and scoring just 173. After going 51-111 last year, the Diamondbacks entered last night’s game at Houston tied for first place in the NL West. How have they done it?

The first thing to look for when a team has dramatically outplayed its run differential is a phenomenal record in one run games. It’s not there: The Diamondbacks are 9-6 in one run affairs, a near match for their .561 overall winning percentage. But take a look at the other end of the spectrum.

In games decided by at least seven runs, the Diamondbacks are 0-4.That’s four blowout losses (8-1, 16-6, 16-2, and 18-3) for a net of -46 runs. They have no blowout wins, so those four games are distorting their run differential. That discrepancy has been exacerbated by a horrible back end of the bullpen. The Snakes have five relievers who have made at least four appearances and posted an ERA of at least 8.31, plus Greg Aquino’s sole contribution of the year, a four-run inning against the Cubs on Opening Day. The 16-2 loss to the Pirates? A Kerry Ligtenberg one-inning, seven-run meltdown. Rockies win 18-3? Ligtenberg again (five runs in 1 2 /3 innings) and Javier Lopez (five runs in 2 /3 of an inning).

Over a full season, the difference between runs scored and allowed is a pretty good barometer of a team’s quality. In shorter time frames, however, a few very good or very poor performances can be deceiving. In the Diamondbacks’ case, their -20 run differential owes not to their core talent, but to fringe pitchers who are unlikely to play down the stretch if the team does contend. The work of Ligtenberg, Lopez, Aquino, and Mike Gosling points to a need to shore up the bullpen, certainly, but doesn’t reflect Arizona’s overall quality.

Run differential aside, the Diamondbacks have already reached nearly half of last season’s win total. Several players are responsible for this resurgence. Luis Gonzalez is unlikely to ever regain his 50-homer power of old, but he’s healthy again and has posted an excellent batting line of .308 AVG/.402 OBA/.469 SLG. Craig Counsell leads NL leadoff hitters in OBA at .428 – his two-year, $2.8 million contract looks like a steal compared to off-season deals signed by Orlando Cabrera, Edgar Renteria, and David Eckstein.

The Diamondbacks’ higher-priced acquisitions have been a mixed bag. When the team signed Troy Glaus to a four-year, $45 million deal in the off-season, no one doubted the slugger’s prodigious power or on-base ability; rather, a right shoulder injury cast into doubt his ability to play third base every day. For now, a healthy Glaus is a good deal – he’s hitting .281/.384/.630 with a league-leading 11 homers.

The $30 million contract extension the team gave Shawn Green after acquiring him from the Dodgers had a smaller shot at success. Green suffers from shoulder problems himself; he’s also four years older than Glaus, and clearly on the downside of his career after peaking in 2001 and 2002. His .253/.309/.390 line this year has hurt Arizona’s offense.

The Diamondbacks also possess a strong, durable rotation that was made over in the wake of Randy Johnson’s departure. Having rediscovered the velocity that made him an elite pitcher in Montreal, Javier Vazquez (4.41 ERA) has struck out a batter an inning so far this year, with a 51/8 K/BB rate. Brandon Webb (3.48 ERA) has also rediscovered his 2003 form, yielding more than four groundballs for every fly ball – the highest ratio in the majors. So far, Brad Halsey (3.88 ERA) has also been a pleasant surprise. Though lacking overpowering stuff, he’s exhibited pinpoint control in his first season as a full-time starter. Shawn Estes, too, has been useful with a 3.83 ERA in eight starts, though he will likely regress.

Like the offense, all is not perfect on the pitching staff. Here, too, the D-backs spent unwisely in the off-season, inking Russ Ortiz to a four-year, $33 million contract. So far, Ortiz seems to have confirmed that the deal is a bust, posting a 4.91 ERA, walking 22, and striking out only 21 in 44 innings.

The team’s deficiencies run deeper still. The D-backs are absolutely awful at shortstop, barely replacement level at catcher, and have deficiencies at first base and wherever Jose Cruz Jr. isn’t playing in the outfield. The bench is bad, and even the relievers who have been good so far – Lance Cormier, Brandon Lyon – are hardly locks to keep pitching well.

Another thing to consider is that there’s virtually no precedent for a team as bad as the 2004 D-backs rocketing into contention the following year. In the era of 162-game seasons, 15 teams have finished with 54 or fewer wins, and just two finished above .500 the following year. One, the 1980 A’s, added one of the greatest short-term managers (Billy Martin) and the greatest leadoff hitter (Rickey Henderson) in baseball history, neither of whom are showing up in Phoenix anytime soon. The other, the 1989 Orioles, were something of a fluke, but the highly underrated Frank Robinson had his trademarks all over it – he gave Randy Milligan and Mickey Tettleton jobs and got good work from a no-name bullpen.

Neither history nor talent level are on the Snakes’ side. Baseball Prospectus’s Pecota system projected Arizona to win 75 games this year; even with the club’s hot start, the talent isn’t there for a record much above .500. Longterm, the contracts given to Glaus, Green, and Ortiz could hurt the team’s ability to construct a winner. On the other hand, top prospects such as Conor Jackson and Carlos Quentin should inject life – and wins – to the nucleus. Like the Diamondbacks’ present, their future remains uncertain.

Mr. Keri writes for Baseball Prospectus. Additional research for this article was contributed by Joe Sheehan. For more state-of-the-art content, visit BaseballProspectus.com.