FORT MYERS, Fla. — At the beginning of spring training in 2025, the Red Sox approached unsettled situations at second base and third base with a pretty good hunch of how things would turn out. Craig Breslow, Alex Cora and the club’s other decision-makers pretty much knew from the time the club signed Alex Bregman that Bregman would play third base and rookie Kristian Campbell would make the team as the starter at second. Campbell had to earn it, though, and there was also the desire to slow-play Rafael Devers’ ill-fated shift to designated hitter.

A year later, the Sox have openings at both positions again. This time, though, it really seems like they don’t know how things will play out. Barring injuries, Willson Contreras will be at first base and Trevor Story will be at shortstop on Opening Day at Cincinnati. The other half of the infield is up in the air with new trade addition Caleb Durbin and Marcelo Mayer likely to get the lion’s share of playing time with Romy Gonzalez and others, including Isiah Kiner-Falefa, also in the mix.

“We’re not gonna make commitments here position-wise, but we have some talented guys that can play defense,” manager Alex Cora said. “Who it’s gonna be at second, who it’s gonna be at third? We don’t know.”

With Durbin set to arrive in Fort Myers on Wednesday for his first day in a Red Sox uniform, here’s what’s clear about how second base and third base will shake out.

1) The Red Sox view Durbin as an everyday player at one of the spots, but won’t commit to which one.

With Gold Glover Brice Turang installed at second base in Milwaukee, the Brewers used Durbin at third for 1,060 ⅔ innings over 131 games (119 starts) and gave him just three starts (and 43 ⅓ innings) at second base all season. Before that, though, he was primarily a second baseman in the minors, manning a position that fit his 5-foot-7 frame. That Durbin played third base last year doesn’t mean the Red Sox aren’t willing to play him at second. What’s clear is that Cora and chief baseball officer Craig Breslow view Durbin as an everyday player and would prefer to install him at one spot.

“I think he showed last year that he can be a very good everyday player in the big leagues,” Breslow said Monday. “He does a lot of things really, really well. When you think about some of the deficiencies that our team had last year in terms of putting the ball in play, not expanding the strike zone and catching up to fastballs, those are all things that he excels at and we think he’s a really good defender as well.”

The Red Sox plan to work Durbin out at both spots, starting Wednesday, and will likely have him play both positions in camp.

2) Mayer is the key, but he has things to prove, too.

Mayer is a natural shortstop who is blocked at that position in Boston. As a rookie, he logged 248 ⅔ innings over 39 games (28 starts) at third base when Bregman was hurt, plus 57 innings over eight games (7 starts) at second. The Red Sox believe Mayer has the ceiling of an elite defender at both spots.

“He was the third baseman, playing well,” Cora said Tuesday. “For how good Alex is at third base, it seems like we didn’t miss a beat. He played well. When he was at second base, he made all the plays.

“He’s a smart individual, a smart player. Smooth. He makes every play. He can play second, short, third. Defensively, he’s really good.”

Cora acknowledged that exposing Mayer — who he described as “not a utility player” — to three positions in camp was likely too much, so it appears he’ll only play second base and third in Florida. (Kiner-Falefa is the backup shortstop behind Story.) There seems to be a thought within the organization that the Red Sox would rather have Mayer, considered the better defender, at the more impactful defensive position (third base). But again, officials want to see what it looks like for a few weeks before making a decision.

Notably, the Red Sox aren’t promising anything to Mayer, who despite showing flashes of above-average play in his first taste of big league action, was inconsistent with the bat and, perhaps more importantly, once again failed to get through a full season healthy. He’s not expected to suffer any lingering effects from the wrist injury that ended his season in late July but the Red Sox are proceeding with caution when it comes to handing innings to him. The additions of Kiner-Falefa and others illustrate that.

3) Platooning remains an option with Gonzalez, others on the roster.

Cora loves playing matchups and that’ll certainly continue in 2026. Notably, Mayer got just five starts against left-handed starters last year — a development that caught players, including Mayer, by surprise after he was called up — and hit .154 with a .416 OPS and 10 strikeouts in 27 plate appearances.

The Red Sox have an elite lefty-masher on their roster in Gonzalez, who has played both second base and third base before. Expect him to start at one of those spots against most southpaws when healthy (he’s recovering from a shoulder injury that lingered into the offseason). Cora also wants to mix Gonzalez back into the outfield mix and the right-handed hitting Nate Eaton is another candidate to play third, if needed.

“We’ve been platooning in 2018, so I’m not going to say we’re not going to,” Cora admitted. “There are certain guys I want to get at-bats, especially in the outfield. We’ll see how that plays out. In the infield, you’ve got to protect who you’ve got to protect.”

4) Cora wants consistency up the middle.

The Red Sox used six different players at second base alongside Story in 2025. In 2024, 11 different players manned the position, continuing an issue that dates back to the end of Dustin Pedroia’s tenure. Cora believes the revolving door has hurt the infield defense.

“I think consistency is very important,” he said. “I know the value of being versatile but having the second baseman and shortstop play as many games together as possible is very important. You see it on winning teams. Last year, our shortstop did an outstanding job playing a lot. At second, obviously, with the ups and downs, it was a revolving door.

As he has in the past, Cora reiterated this week that he thinks a consistent double play combination is crucial to raising the defensive potential of his infield. Therefore, expect a set it-and-forget it type second baseman, at least at first. That may be another clue Durbin is better suited for that spot, especially if Mayer is going to have a platoon partner.

5) There’s plenty of depth, with Kiner-Falefa leading the way.

Cora said he sees Kiner-Falefa playing third base, shortstop, second base and “a little bit” of first base in camp and the ex-Yankee has the ability to play the outfield, too. He’s the first line of defense when it comes to infield depth but he’s not alone as an experienced option.

“He’s really good at second, really good at short and really good at third base defensively,” Cora said of Kiner-Falefa. “That’s something we’ve been trying to accomplish… The edges of the roster, that’s what we’re doing now. That’s what winning teams do.”

Boston’s new-look group of depth infielders — beyond the quartet of Durbin, Mayer, Gonzalez and Kiner-Falefa — includes newcomers Andruw Monasterio, Anthony Seigler and Tsung-Che Cheng as well as Nick Sogard and Nate Eaton on the 40-man roster. There’s also ex-Gold Glover Brendan Rodgers, who was added on a minor league deal. The Red Sox clearly made an effort in the last 10 days to add options that can easily be stashed at Triple-A Worcester. Virtually everyone listed is in that boat.

6) Campbell almost certainly won’t be in the mix.

The Red Sox appear adamant on getting Campbell comfortable in the outfield and playing on the grass will be his focus all spring. As Cora said Tuesday, all of Campbell’s group work and game action will come in the outfield (likely left field) but he’ll continue to do some individual infield drills at both second and third base in an effort to stay ready.

It would likely take a real fire drill-type situation for Campbell to see meaningful innings in the infield in 2026.