PHILADELPHIA (AP) — Phillies ace Zack Wheeler had surgery Monday to remove a blood clot in his upper right arm, and the team says a timeline for his recovery remains uncertain.

The Phillies said Wheeler underwent a thrombolysis procedure by Dr. Paul DiMuzio at Thomas Jefferson University Hospital.

The 35-year-old Wheeler was placed on the 15-day injured list Saturday with a blood clot after experiencing worsening shoulder soreness.

Wheeler, who made his third All-Star team last month, is 10-5 with a 2.71 ERA in 24 starts this season. He has a major league-high 195 strikeouts in 149 2/3 innings. He has thrown at least 192 innings in three of the previous four seasons.