This is not particularly good news for the St. Louis Cardinals:
I'm not convinced that hitting coaches have a measurable impact on teams' fortunes. I think, at best, a hitting coach can make a big difference for an individual player or three. Generally speaking. I'm pretty sure that if hitting coaches had general impact, really smart people would have included hitting coaches in projection systems. And they have not, as far as I know.
So of course it's hard to gauge McGwire's impact on the Cardinals. He took over in 2010. In 2008 and '9, they'd finished with the second- and sixth-best OPS's in the National League. In 2010 they dropped to seventh, but vaulted to first in '11 and settled into third place in '12.
In other words, if you average the two years before McGwire you get fourth place, and if you average the three years with McGwire you get fourth place. All we can really say for sure is that the Cardinals hit well with McGwire, and we don't know that they'll hit well without him ... But then again, we could have said (and I did say) almost exactly the same thing about the Cardinals' new manager and the Cardinals' new pitching coach this season, and they seemed to do well enough. So if you're forced to make a bet, the safe money's probably on the Cardinals ranking ... oh, somewhere not far from fourth in the league next season.
Meanwhile, over the last three seasons the Los Angeles Dodgers have ranked 12th, 10th, and 13th in the National League in OPS. Which I mention because everyone's assuming McGwire has left the Cardinals for the Dodgers, although that's not official yet. Part of the Dodgers' problem is Dodger Stadium, which is friendlier to pitchers than hitters. But part of it's been that their hitters -- with the notable exceptions of Andre Ethier and Matt Kemp -- much good. Adrian Gonzalez will obviously help, and maybe Hanley Ramirez. But the Dodgers need to get better. McGwire's comeback as a baseball man has been impressive. But it'll be a lot more impressive if the Dodgers rank among the league's better-hitting clubs in 2013.