Homer Bailey has been an undercover star for the Oakland A’s

Entering the season, Homer Bailey was an afterthought. After four years of struggling with injuries and ineffectiveness, the Reds traded him to the Dodgers in a salary dump, at which point L.A. released him. The Dodgers are paying him more than $22 million to not pitch for them, and this spring he wound up signing a minor league contract with the rebuilding Royals.

Since then, Bailey has bounced back in a big way. He turned in a league-average performance in 18 starts for Kansas City, which was already a big step up from what he’d done the previous few years, and that work earned him a trade to a contender in July. The A’s took a chance on him at the low price of one mostly busted prospect, and that swap is turning out to be an absolute steal for Oakland.

Bailey has made 12 starts for the A’s, and his overall numbers might seem pedestrian at first glance:

Bailey, OAK: 4.21 ERA, 68⅓ ip, 65 Ks, 15 BB, 9 HR

Look beyond the mediocre ERA, though, and you’ll see a strong 3.77 FIP, which is nearly a run better than any other A’s starter right now except for the tiny sample of Sean Manaea. That mark comes from striking out nearly a batter per inning and more than four batters per walk, and those peripherals have him worth 1.5 fWAR in around one-third of a season’s worth of work.

And what about that ERA? In his second outing for the A’s he got blown up by the Astros, allowing nine runs in two innings. That loss counts, but only once, and the shellacking was so extreme that it is skewing his personal numbers far more than that one game skewed the A’s record. Remove it and his line looks like an outright star:

Bailey, OAK (minus 7/22 vs HOU): 3.12 ERA, 66⅓ ip, 63 Ks, 12 BB, 6 HR

Any pitcher would look better if you cherry-picked out his worst game, but not to that extent, with that extreme of a beatdown confounding a partial-season sample. And it’s not pure fantasy to give him a mulligan for his huge loss, as he returned to Houston in September and beat them in the rematch, pitching into the 6th inning and allowing just one run. For 11 of his 12 starts he’s been the monster in that second stat line above, and he atoned for the one time he got crushed by the most stacked lineup in the majors.

Here’s another way to put it: In those 11 starts, he was almost Frankie Montas. The ERA is close (Montas was at 2.70), and Bailey’s prorated FIP would be around 3.07 (Montas was at 2.90), with a similar innings average and strikeout/walk rates. Statcast agrees, giving Bailey a sparkling xwOBA of .295 even including the bad Houston game, not far from the .270 mark of Montas. The comparison is especially appropriate considering that Bailey arrived just a few weeks after Montas was suspended — he essentially plugged into the spot vacated by Oakland’s ace, lost one big blowout to the Astros, and then did his best impression of that missing ace for two-plus months.

Furthermore, Bailey hasn’t just padded his stats against weak opponents. In addition to his two games against AL-best Houston, he also faced the juggernaut Yankees twice and held his own both times, and put in a quality effort against the Wild Card-contending Brewers. The only other time he got lit up was by the then-division-leading Cubs in Wrigley, where they’ve got the fourth-best home record in the majors. Even his matchup against the Giants came when they were still playing decent ball and hitting around average.

In other words, a third of Bailey’s starts have come against the AL’s elite, and a full half of them against playoff contenders. The rest were against the Mariners, Rangers, Tigers, and two against his old Royals teammates, so he’s also gotten his share of relatively easier assignments, but he’s faced enough real tests to take him seriously. Seven of his 12 appearances registered as quality starts, and two more (the ones against the Yankees) fell just one out short — he’s been good for 6-7 strong innings against bad teams, and 5+ strong against good teams.

In particular, Bailey’s splitter has been phenomenal. It’s earned him a ton of swinging strikes, and when batters do make contact they aren’t doing much with it. On Wednesday, amid seven dominant shutout innings against the Royals, he got 11 swinging strikes with that pitch, including the final whiff on seven of his 11 strikeouts. At one point he struck out five out of six batters swinging on the splitter, including four batters in a row.

Here’s a look at the pitch from Wednesday, though there are also a couple four-seamers and sliders mixed in (first one is a splitter, then two heaters, then a slider, then six straight splitters, then a slider):

The A’s rotation has been a pleasant surprise this season. They entered with low expectations and then lost their biggest success story in June, and yet they rank as one of the better units in the league, helping to anchor a team contending for the postseason. Mike Fiers, Brett Anderson, and Chris Bassitt have all panned out again as consistent producers, Tanner Roark has put in the quality work expected of his notable trade price, and Sean Manaea has burst back onto the scene this month after a long-term injury layoff.

But Bailey, a forgotten man just months ago, has been the biggest shock of all. He came to town with no fanfare, and at virtually no cost, but he’s been arguably the team’s best starter since the All-Star break. He’s the latest poster boy for Oakland’s resilient, odds-defying, misfit-toy rotation, and he’s performed like a star even if his ERA doesn’t fully show it.