That concern has not entirely gone away. From Wacha's
Fangraphs page.
2022 ERA: 2.44 2022 xERA: 4.77 (FYI, BaseballSavant has his xERA as 4.43)
(FWIW, his FIP is 3.7 and xFIP is 4.09)
What is xERA? Also from Fangraphs:
xERA uses exit velocity, launch angle, and sprint speed on “topped” or “weakly hit” balls to model what a player’s ERA would look like based on the underlying characteristics of the balls in play.
He's also running a .234 BABIP
So yes, there's a decent amount in the underlying metrics that suggest he's getting lucky. He's having sort of a weird season, in many ways. Compared to his previous 2 (ineffective) seasons, he's striking out fewer and walking more batters, which seems like an unlikely recipe for success. But he's giving up wayyyy fewer HR than those seasons: his HR/9 has gone from 2.38-->1.66-->0.81
How is he doing it? Taking a look at some of his other metrics on BaseballSavant...shows he's giving up fewer barrels than in the last couple of years, has somewhat increased his % of balls listed as "under" but nothing really stands out. I think Wacha continues to be who he has often been---a decent pitcher whose success is highly tied to how often his fly balls leave the yard. With the deadened baseball this year, he's picked an excellent time to be that sort of pitcher. He's almost certainly not as good as his ERA would indicate---maybe he's figured something out to help him reduce some of his hard FB contact, but some of it is almost certainly luck. But hey, that's the nature of baseball---the last couple of years he underperformed his metrics. In baseball there's a lot of disconnect between "process" (be it underlying batted ball stats for hitters/pitchers or the front offices strategy in building a team) vs. "results" (actual batted ball outcomes and...actual performance of players). I wouldn't want to extend him a contract that assumed his true talent level was a ~2.5 ERA but at the end of the day, the results he's gotten are the results he's gotten, same as for any player. My guess is that going forward he's about as likely to put up a ~3 ERA as ~5 but that shouldn't take away from the great season he has had.