“It’s a significant knee injury. He’s at the hospital right now getting more tests and all that stuff,” Red Sox manager Alex Cora told reporters, as seen on NESN’s postgame coverage. “We’ll have more information tomorrow.”

Cora added that when he went out to the field with the trainers, he believed Casas was “in shock” as he lay on the ground being evaluated.

“He said right away that he didn’t feel it,” Cora said. “It’s tough. He worked so hard, and we wanted him on the field to play, too. And that happened. You put so much effort into the offseason. … Everything that he went through in the offseason, getting ready for this (season), he was looking forward to having a big season for us.

“He didn’t start it the way he wanted, but he kept running, kept working. And now this happened. We love this. We love the whole thing. But, in the end, we’re human beings, and you suffer. You suffer with them. It was tough to see him.”

Cora admitted it’s never easy to see a player get injured during a game.

“It sucks to be honest with you,” he said. “That’s the part that you don’t like about the job, right? When people get hurt, and you have to send people down (to the minors). It’s pretty tough because you’re afraid to play 162-plus, and then something like this happens.

“That’s the reason we don’t take it for granted either. Showing up to work every day and being a big leaguer. He loves being a big leaguer. He loves it. … For now, I think it’s going to be taken away, but I told him, he’s going to be back at one point. … When you see the cart, that’s when you’re like, ‘Oh, this is more than just a twisted ankle.’”

Casas played just 63 games for Boston last season, missing most of the campaign with a rib injury. He slashed .184/.279/.306 with three home runs and 11 RBIs in 29 games this season.