One of the best relievers in baseball might have his season in jeopardy.

The Baltimore Orioles placed All-Star closer Félix Bautista on the 15-day injured list due to a right UCL injury, the team announced Saturday. The move came a day after the right-hander exited a game due to what was described as arm discomfort.

Left-hander DL Hall, a top-100 prospect before the season, was recalled from Triple-A in a corresponding move.

The Orioles were hazy about the extent of Bautista's injury, with general manager Mike Elias tell reporters only that he had "some degree of injury." A UCL injury is often followed by Tommy John surgery, but this could also be a minor issue.

The injury interrupts what had been a breakout season for Bautista, who has closed 33 of 39 games for the first-place Orioles. The hulking, 6-foot-8, 285-pounder's 1.48 ERA is the best in the American League among pitchers with at least 50 innings pitched, ranking behind only Brusdar Graterol of the Los Angeles Dodgers for the MLB lead. His 46.4% strikeout rate is easily the best in the majors, more than eight points ahead of second-place Spencer Strider of the Atlanta Braves.

With Bautista out, Yennier Canó and his 1.62 ERA are the natural choice for the replacement as closer, but the Orioles can only hope Bautista will be back on the mound come playoff time.