Santana was injured when he was involved in a violent collision at home plate in the Indians' 6-5 victory over the Red Sox on Monday night at Fenway Park.
"He tested well with the trainers, meaning they don't feel he has any serious damage -- his ACL or anything like that," manager Manny Acta said. "He is leaving tomorrow for Cleveland to get an MRI."
With one out in the seventh inning, Boston's Ryan Kalish was attempting to score from second base on a single to right field by pinch-hitter Daniel Nava. Shin-Soo Choo threw a strike to home plate, where Santana had his left leg extended to block the dish.
Kalish plowed into Santana's left leg and was tagged out, and both players went sprawling around home plate. While the backstop held onto the ball for the second out of the inning, he immediately fell to the ground in pain.
After Indians trainers, coaches and players stood around him as he was examined for more than 10 minutes, Santana had his left leg placed in an orange air cast and was carted off the field.
"I mean, obviously, I feel bad. He's blocking the plate and I thought I had enough time to get in there with my foot," Kalish said. "It's a hard slide. I've already talked to him. He says he's doing a lot better than he thought and I feel awful. You can't feel good about something like that. It's part of the game. It happened."
Kalish made sure to talk with Santana, who wasn't taken to a local hospital, after the game and tell him how much the play was on his mind.
"I just told him, 'Hey man, I'm thinking about you,'" Kalish said. "I'm sorry about what happened obviously. It's part of the game. Hopefully I'll keep in touch and see how he's doing."
Santana, who wasn't made available to the media, was replaced behind the plate by Chris Gimenez.
"You don't want the worst-case scenario to happen with him," left fielder Shelley Duncan said. "We will hold our breath."
Quinn Roberts is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.