MASHANTUCKET, Conn. — The mystery player the Red Sox talked to about an extension earlier this offseason was Xander Bogaerts, multiple sources said. The conversations never heated up or brought the sides close to a deal, but the Red Sox and Bogaerts’ agency, Scott Boras’ camp, did engage on the matter.

Bogaerts can become a free agent after this season and quietly had a tremendous year in 2018, one that probably slipped under the radar as Mookie Betts became the MVP and J.D. Martinez had a hit seemingly every night. The shortstop hit .288 with a .360 on-base percentage, .522 slugging percentage and 23 home runs.

Bogaerts and the Sox recently avoided arbitration by settling on a one-year, $12 million contract.

NBC Sports Boston previously reported the Red Sox were talking to a core player about an extension, but it wasn’t clear who. Some in the industry speculated at the time it was Andrew Benintendi, Benintendi said Saturday he hasn’t had talks with the team, and sources have confirmed Bogaerts was, in fact, the player.

Whether the Sox get a deal done with any of their top players remains a matter to watch this winter. Chris Sale confirmed at Winter Weekend that he’s open to an extension.

“My phone is on if they call me,” Sale said. "Obviously, nothing has happened up until this point. If they call, I’d answer.”

The Red Sox are being and have been very forward that they want to keep Mookie Betts, as well as their other stars.

“He’s the exact type of player you want to have on your team, not just from what he does on the field but off the field,” Sox president and CEO Sam Kennedy said Saturday at Winter Weekend. “He’s such a great person and we’d love to have him be a Red Sox for his entire career. Certainly understand, you try to put yourself in the other person’s shoes, he’s going to want to see what the market looks like and understand that. But we’ve made it crystal clear that we want him a part of the Red Sox organization long term.

“I don’t know why a player would ever want to play anywhere else other than Boston. That comes from a very biased person. I’m a Bostonian. But you look around at the fan support, you look at this ownership group. The commitment to winning, the great history and tradition. Talk to a lot of alums who have been here and gone other places. And I just, I think a lot of ‘em wish they had stayed in Boston and finished their careers here. We’re now approaching a 20-year run of an era in Boston sports unlike any other in the history of professional sports. This is where you want to be.”

Said Bogaerts on the outlook from here: "I mean, always if both sides can get to an agreement to a point...I don't see no wrong with that. But I mean if the price is right, I guess, for both sides, I think it's always fair enough for anyone who's open to talk."

As for Betts, the reality may be simple: get to the market, and see what’s out there, or maybe take a deal from the Red Sox if it appears to be equivalent to what he would get on the open market. At this point, with Bryce Harper and Manny Machado both unsigned, it’s hard to know exactly how high Betts value could go when he's a free agent after the 2020 season.

“Contract things are kind of tough to come up with, especially with both sides and kind of how the economics and all those things work,” Betts said Saturday. “I love Boston, love my teammates, love the fans and all those types of things, so we’ll just continue to see what happens.”

Betts made clear he knows how free agency appears to be unfolding, but at the same time, said nothing that indicates he wants to avoid it, or that he thinks it’s anything other than his best route.

“It’s not just those two, there’s a lot of good guys still out there that haven’t signed,” Betts said. “Kind of cross that bridge as we come to it. There’s a lot of good guys that are unsigned, and there shouldn’t be.”

Sox president of baseball operations Dave Dombrowski has said he prefers to get extensions before the regular season, be it in the offseason or spring training. Asked if he sees talks with the Sox coming soon, Betts said he lets his agents handle it.

Sox owner John Henry noted on Friday that extensions for younger players seem less prevalent these days.

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