The Red Sox have four major free agent decisions to make this winter, and the bet here is that you can name three of them immediately.

There’s Jacoby Ellsbury, of course. He’ll end up being one of the highest-paid players on the market. There’s also first baseman Mike Napoli, who is turning on the power in September, as well as steady shortstop Stephen Drew, a player more respected by management and the coaching staff necessarily than the fans.

All three are good bets to receive qualifying offers somewhere in the vicinity of $14 million. Any who accept will be back next season. Those who don’t and sign elsewhere will garner the Sox a draft pick.

But there’s a fourth candidate for that designation, too — and before you scoff, consider the kind of season Jarrod Saltalamacchia has put together.

The switch-hitting catcher blasted the game-winning grand slam in the seventh inning of an 8-4 victory over the Yankees last night. He’s not going to match last year’s career high of 25 homers, but he has improved his game in pretty much every other way — be it hits (103), doubles (36), or OPS (.788), not to mention behind the plate.

So while the playoffs may be first and foremost on everyone’s mind, the Sox must already be formulating their plan for the offseason. And the more you think about it, the more likely it seems that Salty is a part of it.

“Guys like him don’t come around, guys that can catch and hit for that kind of power,” said backup catcher David Ross. “I think he was very underrated coming into this year, and he’s really come into his own. What did he hit last year, 25 homers? Those guys aren’t around anymore. Those guys are hard to find. It’s definitely a commodity.

“Everyone in here knows how special he is. The public may not know, but everyone in here knows how big a part of the puzzle he is.”

Saltalamacchia played the part of hero last night. He had already walked, doubled and scored a run when he stepped in against Yankees reliever Preston Claiborne in the seventh with one out and the bases loaded.

Claiborne had featured an effective changeup that sailed down, away and right off the plate while striking out the previous hitter, Daniel Nava, so Saltalamacchia took note and looked for something over the plate.

“I was really just trying to get a good pitch to hit in the air,” he said. “I knew I had (Shane) Vic(torino) at third, fast guy, so if I put it somewhere out in the air he was going to be able to score. I saw how he had pitched Nava. I knew he had good stuff, I’d only faced him once, so I didn’t have a lot of experience with him. I just needed to get a strike up in the zone to do something with.”

He took a changeup for a borderline strike and then unloaded on a 92 mph fastball, launching it over the fence in right.

“He crushes balls,” Ross said. “When he hits them, they’re not cheap. I was just talking to David (Ortiz). When the ball comes off his bat, it’s a thonk. Some guys just hit them and they don’t sound as loud and then they go further than anybody’s. That’s him.”

Saltalamacchia has improved behind the plate — starter John Lackey last night credited him for running the advance meetings confidently — and he has proven an ability to assume an increased workload, thanks to the two-plus months Ross missed with a concussion.

His OPS ranks among the top 10 catchers in baseball, and he’s exactly the kind of player the Red Sox would pursue on the open market if he came free from another team.

That’s not an issue, however, since he’s already here. And the way he’s going, he’s looking more and more like a keeper.