Martín Pérez took the mound at Fenway Park Friday night looking to snap the White Sox four four-game losing streak. By the end of the night, he was in the visitors’ clubhouse being evaluated after a 10-3 blowout loss to the Red Sox.

Pérez made it through three innings, allowing four runs on five hits with a pair of walks and no strikeouts. But after just 52 pitches, he left the game with left forearm soreness.

Losing Pérez would deal a significant blow to the White Sox pitching staff. The 34-year-old left-hander is the oldest member of a rotation that averages just 27 years old. A 14-year MLB veteran, Pérez was signed in the offseason to provide leadership and stability while shouldering a consistent workload.

Through his first four starts, Pérez has quickly established himself as one of the team’s most effective starters, posting a 1-1 record with a 3.15 ERA. He leads the rotation in innings pitched (22.1), WHIP (1.25), and opponent batting average (.197), all without throwing a pitch over 90 mph. Pérez also tops the staff with 18 strikeouts.

Early on in Friday’s outing, there were signs that Pérez was off. Red Sox hitters teed off on him early, jumping to a quick 3-0 lead courtesy of a run shot off the bat of Trevor Story.  Pérez then needed a ground ball to escape the first inning with runners on first and second without further damage.

The Red Sox added another run in the third, with Pérez ending the inning—and his night—by getting Kristen Campbell to fly out to center on an 87 mph sinker. The White Sox have yet to announce if Pérez will need to spend time on the injured list.

His next start is scheduled for April 23rd in Minnesota.