Britton struck out the first two batters he faced, but came up limping after fielding a drag bunt by White Sox right fielder Adam Eaton.
Britton scooped the ball near first base and attempted to flip it out of his glove to first baseman Chris Davis. But Eaton was safe and trainers came out to check on Britton after the play.
Manager Buck Showalter said after the game that he didn't know the severity of the injury.
"We’ll see how it is tomorrow," Showalter said. "[Head athletic trainer Richie Bancells] and them were looking at the replay and talking. He had jammed it more than rolled it. I’m sure you all saw the replay, too. The proverbial day-to-day. We’ll see what tomorrow brings. Zach has always been a pretty quick healer, so we’ll see."
Britton briefly stepped onto the mound to try and test his leg, but didn't throw a warmup pitch and walked off the mound. Vance Worley replaced Britton out of the bullpen.
The play in question was reminiscent of Britton's game-ending play Friday, when he fielded a ball and dove to tag Avisail Garcia for the final out of a 6-3 win over Chicago.
"I’ll tell you, Zach has come so far as a defender," Showalter said. "When he first started, his first year or two it was a real challenge for him. He worked so hard on it to become a really quality defender, and almost made a great play tonight."
Eaton eventually scored to put the White Sox ahead, 8-7, Saturday. Britton was ultimately charged with a run and the loss.
Reliever Darren O'Day called Saturday a "poor performance by the bullpen," as he, Britton, and Mychal Givens combined to allow five runs in the loss.
O'Day didn't see Britton's injury, but said the sinker-heavy arsenal he has dictates he makes more plays than a normal pitcher.
"Zach, he has to run all over the field," O'Day said. "He makes a lot of athletic plays just because of the kind of contact his sinker produces. So Zach’s worked really hard to make himself an above-average fielder. I’m sure he’ll be fine. He’s a tough guy so, we’ll find out more about that."
Britton, the Orioles' All-Star closer, entered the game with a 1.93 ERA and six saves, with 11 strikeouts in 9 1/3 innings.
When asked if the news he got after the game was better than he'd expected having watched the play, Showalter said, "sure," but tried to downplay any potential injury's impact.
"We’re going to have challenges during the year," Showalter said. "We’ve got people, just like we had tonight. We did a lot of good things tonight. But I’m not one of those guys, you know, when something happens -- we’ll deal with it. We’ll deal with it, and our club knows that."