As Melvin Upton steps to the plate and readies for the pitch, Buster Posey appraises him. First, he looks at his feet as they dig in. Gradually, his eyes move up Upton’s body, brazenly staring as he takes in information. Down pops the sign as the catcher moves his attention to the pitcher.

It’s not just idle ogling. He’s looking for clues. Which ones?

Brandon Moss thought the most likely thing was that the catcher is looking for a change in approach, particularly due to count. “I’d never tell anyone my two-strike approach,” he told me when I asked him what he did to make more contact. “We all know when we have to make a small adjustment to get a pitcher off a spot. I think the catcher can see it. They watch the hitter get in the box with their feet. They’re seeing what you’re doing, they always watch.”

They’re mostly watching the feet. Chris Iannetta remembered figuring out what one veteran did with his feet: “Paul Konerko would open up his back foot towards right field when he was trying to go opposite field, and when he wanted to pull the ball, he’d close it.” If you want to try to simulate this at home, imagine you are a right-hander. Make your back foot perpendicular to the pitcher’s mound, and then open up your toe so that your foot is now parallel with the right-field wall. Your body is now lined up to power pitches to right field.

Knowing that sort of thing can be super helpful to calling the game, and there is other foot-based scouting the catcher can do. Are they inching up in the box after an offspeed pitch? Are they backing away from the plate after getting busted inside? What is their body language like after certain pitches?

But you can go too far. “Some guys move up on the plate if the pitcher has a good offspeed pitch, but they might be setting you up, too, to make you think that,” said Iannetta. Former teammate Hank Conger agreed. “They’ll inch way up, hoping I’ll think I can blow a heater by him because he’s sitting curveball,” he said. “But they’ll really be sitting fastball.” Moss detailed just this sort of thing, as well.

It can get confusing on both sides of the ball. Colby Rasmus has been experimenting with different stances at the plate, and apparently it has something to do with this in-game scouting from the catcher. “I wanted to try and hit some balls the other way because we have that short porch in Houston, with the boxes out there,” Rasmus said, “so, at the beginning of the year, I tried to work my swing to go the other way.”

He pulled two-thirds of the balls he saw in April. The plan didn’t work, maybe. Or maybe “pitchers are smart,” as he put it. “When you close off and try to go the other way, they can see that, so they started throwing some balls in.” He agreed it was the catcher that probably spotted it. “They have the privilege of waiting on you to do what you’re going to do. It’s tough.” He’s in the middle of alternating opened and closed stances, with some stances that close as the pitch comes in. “It’s kind of a chess match,” Rasmus says, although it’s a bewildering one in his case.

What do you do with the information you get if some of the information is not helpful? “I try to take everything with a grain of salt,” shrugged Conger. “You’re playing poker,” smiled Iannetta dryly, “a game within a game.”

Conger did think you might be able to spot smaller changes that might be authentic. “There are some guys where, like if we’ve been pounding them in with a two-seam, they’ll just slowly move their feet,” the Houston catcher said. “They’ll be an inch or two backed off. I always check the feet.”

In the end, just looking a the batter might be a worthy enterprise. You could make the batter nervous and make him think about something other than his normal approach at the plate. “Even if I don’t see anything there,” Conger smiled, “I’ll look anyway to make them think I’m noticing something in their feet.”

Poker, maybe, but on a field, and mostly involving intricate foot positions and possibly faked body language.