A number of factors dictate pitch selection. Scouting reports and reads play a role — as do game situations, counts and repertoires. Some pitchers are more predictable than others — often to their detriment — but once the starter has delivered his first pitch in a game, it becomes a chess match.

The game’s first pitch isn’t unpredictable. According to Jeff Zimmerman’s research, 95.6% of all first pitches thrown in 2012 and 2013 have been fastballs. Of those pitches, 51.1% have been taken for strike, 35.9% have been taken for a ball and 13.1% have been swung at.

Overall, hitters have seen a fastball 63.5% of the time. Of all pitches thrown, 36% have been taken for a ball, 17.9% have been taken for a strike and 46.1% have been swung at.

A.J. Pierzynski probably doesn’t know all of those numbers, but having spent over 1,600 big-league games behind the plate, he has a pretty good idea of how the pitch-selection chess match works. The Texas Rangers catcher weighed in on the subject earlier this month at Fenway Park.

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Pierzynski on the game’s first pitch: “There are occasions, like with a Derek Jeter, where we’ll throw a slider. We’ll throw fastballs in to certain guys. But other than that, it’s usually always a fastball away. You want to try to get the pitcher into a rhythm, and comfortable. He doesn’t come out thinking, ‘I’m going to throw a slider’ — or something off-speed — unless we talked about it before the game.

“In most cases, it’s generally accepted that the hitter is going to take the first pitch. That’s unless it’s maybe a guy like Jeter, or Gerardo Parra from the Diamondbacks; he swings a lot at first pitches. There are a few guys now who have started to swing at the first pitch of a game.”

On in-game adjustments: “Before the game, we’ll talk about the first couple of hitters and what we want to do against them. Then we go from there. Before every series we go over every hitter, and every day we sit down with the starter to go through it. You’re always talking about it and you’re always changing — you’re making in-game adjustments. Guys make adjustments at the plate and you have to adjust to what he’s doing — make adjustments off your game plan. You have to try to stay ahead of the curve.

“You’re adjusting right away. When Jacoby Ellsbury comes up to hit tonight, we’re going to see what his approach is and we’ll work our way down from there. Each at bat takes shape; it takes a form of its own. That’s what baseball is built on. Situations are ever-changing and there are intangibles.

“Sometimes a pitcher comes out of the bullpen and says, ‘Hey, I know we talked about attacking this guy with this pitch, but I don’t have a good feel for it; let’s try something different.’ And you can watch a guy warm up and see he doesn’t have a good feel for something, but you still might try to get him to throw it to find that feel. It changes. Guys like [Yu] Darvish and [Derek] Holland, we talk about it. It’s ‘We’re going to attack a guy like this,’ and then we get into the second inning — or the second time through the order — and they’ll be like, ‘Hey, I don’t feel this pitch, let’s do something different.’ It happens all the time.”

On being on the same page: “Early in the game, the pitcher and catcher are usually always on the same page, because you’ve talked about it. But if you’re not, once you get through an inning you sit down on the bench and talk. Or maybe I’ll go out to the mound so we can talk about what he sees and what I see. It’s not an exact science; it’s something that’s hard to quantify.

“There are all these different defensive things they try to measure, but how do measure what actually happens in a game with a pitcher and a catcher? Things changes pitch to pitch, inning to inning, game to game, day to day. It’s never the same, so it’s not an easy thing to put your finger on. As a catcher, it’s not easy to always be on the exact same page as your pitcher. When you are, those are the special days.”