This past offseason, a lot of discussion took place about Miguel Gonzalez’s tendency to overperform his FIP, meaning, to produce an ERA lower than his FIP. Each year a handful of pitchers’ ERAs differ from their FIPs by some degree. Gonzalez did so to an exceptional degree last year, as did the rest of the Orioles rotation. On the whole, the staff outperformed its FIP by nearly six wins, the 8th-highest mark any team has achieved in the past 20 years.

This year, not only is Miguel Gonzalez outperforming his FIP again, but he’s being outclassed in this respect by his rotation-mate Wei-Yin Chen. Through Monday’s game, here is the leaderboard for qualified starters’ ERA-FIP overperformance, measured in runs:

Compare this list with a ranking of the same starters on K-BB%. You'll find Chen ranked 35th and Gonzalez ranked 56th.





So far this year, Gonazlez’s overperformance has been worth one win to the team, while Chen’s has been worth nearly two wins. Given the tight separation in the AL East this year, those wins really matter to the team and its fans.

As you might imagine, both pitchers are running a low BABIP. Chen’s BABIP is .248, which ranks 7th-lowest among the 96 qualified starters this year. Gonzalez isn’t too far behind him at .253 (9th-lowest), but his career mark is .264. Gonzalez has always run out a low BABIP, so it’s not that surprising to see him with such a low mark this year. But prior to this year, Chen's BABIP was a normal-looking .291, making the drop to .248 positively astonishing.

The fall in BABIP is somewhat explained by an increase in flyball rate. Chen’s rate of 42% is 9th-highest in the league. He hasn’t run a flyball rate this high since his debut in 2012. Gonzalez is also running a high flyball rate; his mark of 37.4% ranks 23rd. But this is below his career rate of 41.5%.

According to Inside Edge quality-of-contact data, both pitchers have excelled at preventing hard-hit balls this year. Chen’s Hard% is just 25.1%, 14th-best among starters. Gonzalez isn’t far behind with a Hard% of 26.1%, 18th-best. Chen has lowered his Hard% each year since 2013, while Gonzalez’s hard-hit rate has bounced around a bit.

Finally, good defense is playing a role in these pitchers’ success. FanGraphs’ aggregate defensive rating (Def), which is UZR combined with a positional adjustment, has the Orioles defenders saving 14.5 runs more than the average team. That mark is 4th-best in the sport. The team has very good defenders at shortstop (ranked 4th in Def), third base (4th), center field (9th), and left field (3rd). They've got the left side of the infield covered as well as two of the four up-the-middle positions. Those fast feet and strong arms will tend to depress the BABIP of the man on the mound.

Of the other mainstay Orioles starters this year, only Ubaldo Jimenez is overperforming his FIP, but he’s only doing so by three runs. Interestingly, despite pitching in front of the same defense as Gonzalez and Chen and despite being even more of a flyball pitcher than Gonzalez, Chris Tillman is underperforming his FIP, and that FIP is better than Gonzalez's. Meanwhile, sad Bud Norris is underperforming his FIP also, but that FIP is so bad (5.43) that it’s not worth diving into.

Chen and Gonzalez are two good examples of what can work when Dan Duquette acquires low- to mid-tier starting pitchers and puts them in front of a superlative defense, lockdown bullpen, and good offense. Unfortunately, Tillman and Norris serve as counterexamples. But it’s interesting to see how it looks when it all goes right. The 2015 Orioles certainly have relied on Chen and Gonzalez and will continue to do so in the dogfight that is the AL East this year.

On a sad note, as I write this, the Orioles lost to Kyle Gibson, who ranks two spots below Chen on the ERA-FIP overperformance list above.

All data for this post taken from FanGraphs.