CHICAGO — In a sport where just about everything can be bottled up into a metric of some kind, a catcher’s impact on his pitching staff may be impossible to measure.

There are framing stats, sure, but that is only part of it. There is the game planning ahead of time, learning everything about the opposing team’s 13 hitters and even more about the 13 pitchers on the catcher’s own staff, knowing what pitch to call when, and how to guide their pitcher through the ups and downs of nine innings on a given night.

So perhaps you will just have to take Gerrit Cole and Max Fried at their word when the veteran pitchers talk about the value of Austin Wells and Ali Sánchez (plus J.C. Escarra earlier this season) on the Yankees pitching staff, which entered Wednesday with the lowest ERA (3.40) in the majors.

“They deserve a lot of credit for the run prevention,” said Cole, who brought up the catchers unprompted after throwing six shutout innings against the White Sox on Tuesday night. “Obviously we have good pitchers, but they’re back there doing a lot of prep for us and making a lot of the right calls and getting us out of jams. It’s been a good team effort overall.”