After two days on the bench, Kristian Campbell returned to the lineup playing center field on Tuesday.

Though the Red Sox rookie didn’t play in Sunday’s finale with the Braves and Monday’s series opener with the Mets, he’s been hard at work throughout this 10-game home stand; his first-base lessons continue as the Red Sox scramble to plug the massive hole left behind by Triston Casas’ season-ending injury earlier this month.

“Flo feels like around the bag he’s moving better,” manager Alex Cora said of first-base coach Jose Flores. “The ground-ball is the ground-ball, right, and we do believe he’s going to make plays, but I think around the bag is the most important thing.”

Campbell, who made his MLB debut on Opening Day, has also been struggling at the plate as pitchers around the league begin to figure him out. But while he entered Tuesday hitting .085 with a .253 OPS in 11 May games, learning a new position also contributed to the decision to give him back-to-back days off. Since the Red Sox began this home stand last Friday, the rookie has already done three sessions of first-base drills, on top of his usual duties.

“I think he has felt, too, the work,” Cora said. “He was a little bit tight on Sunday… so we have to be careful, that’s what you run into, right?

“We’re trying to teach him a new position, he’s learning a position at the big-league level, and now he’s playing center field today. So there’s a lot thrown at him, but I think physically we have to be very careful. We don’t want to lose him just because he’s learning a position.”

Asked how he would grade Campbell’s progress toward playing first base in real games, Cora said on a scale of 10, “probably two and a half, three.” He emphatically shut down the idea that the rookie would make his first-base debut during this home stand, which ends on Sunday.

“We’ll try to get to 10 as soon as possible,” the Sox skipper said, “but being smart about it.”