We’ve gotten significantly better at grading defense this century, specifically catcher’s defense. One attempt at analyzing catcher defense from last century was catchers’ ERA (cERA) which takes the ERA calculation from pitchers but uses it when a catcher is in the game behind the plate. There’s no doubt that cERA has problems – like any statistic – and it’s fine to take it with a grain of salt. For one thing, it doesn’t take account of who was on the mound. It’s a lot easier to have a good cERA if you’re catching 2019 Jacob deGrom than if you’re catching 2023 Carlos Carrasco.
To me, it’s a jumping off point. If you think Catcher X is good/bad but his cERA gives you the opposite answer, perhaps you need to dig in more to both your original assumption about the catcher and why his cERA is the way it is. It could be perfectly reasonable why the cERA rates as it does. Perhaps your good defensive catcher happened to be behind the plate for the 15-run outing the pitching staff had. Perhaps your defensive butcher was on the mound when the pitchers notched 19 strikeouts. Or maybe it’s not so clear. With that in mind, here are the cERAs for the three catchers the Mets have used this season along with opponents’ OPS:
Francisco Alvarez – 38 INN, .728 OPS, 4.26 cERA
Omar Narvaez — 35 INN, .791 OPS, 5.66 cERA
Tomas Nido – 85 INN, .754 OPS, 3.60 cERA
Alvarez comes across pretty good here, with the lowest OPS and a cERA 1.40 rpg better than Narvaez, who was allegedly brought in because of his defense. But here’s where we need to dig a little deeper. With Alvarez, he’s had two starts against the A’s and one each against the Marlins and Padres. The Padres rank 25th in MLB with an average of 3.79 runs per game. The A’s rank 27th (3.50) and the Marlins are 29th (3.17) in MLB in runs.
It was probably fortunate for Alvarez to break in against the teams he did. Yet he had the misfortune of catching Carrasco in two of his four starts, which might explain some of the results, too. And he caught Jose Butto in another. Hopefully Alvarez gets to catch a lot more in the weeks ahead and face good hitting teams and catch guys besides the 5th and 8th starters. And we can see where his cERA stands at that point.
Of course, it won’t really matter unless he starts hitting.