The Kansas City Royals placed right-hander Stephen Kolek on the 15-day injured list on Sunday after he strained his right flexor during a rehab start.

Kolek was injured on Saturday while pitching for Triple-A Omaha to get him ready to return to the major league squad as soon as this week after an extended absence on the family medical emergency list.

He was scheduled for four innings or 65 pitches but made it through only 51 pitches (30 strikes) over 2 2/3 innings against the Lehigh Valley IronPigs before he exited in the third inning with the Omaha Storm Chasers' trainer.

Kolek allowed two runs on six hits with a hit batter, no walks and three strikeouts.

"He said he didn't feel great playing catch, but then as he got on the mound, he felt better," Kansas City manager Matt Quatraro said Sunday. "The first couple of innings were pretty good. In the third inning, he felt more aggressive discomfort. They thought it was best to get him out of there."

Kolek, 29, is scheduled to get imaging done on Monday.

He last pitched in a major league game on July 2, allowing three runs on four hits in two innings of a 5-2 home loss to the Tampa Bay Rays.

Kolek has been away from the team since before the birth of his daughter, Faye, who was born seven weeks premature on June 25, MLB.com reported. He has been in the hospital with his wife, Jessica, and their baby, leaving only for that July 2 start. The Royals placed him on the family emergency medical list three times and the paternity list twice as well as the restricted list on July 11, according to MLB.com.

With his child making progress, Kolek planned to return to the Royals, including Saturday's rehab start. Major League Baseball gave the Royals permission for Kolek to have a rehab assignment, which is not the norm for players on the restricted list.

Kolek is 4-3 with one shutout, a 4.50 ERA, 12 walks and 34 strikeouts in 54 innings over 10 starts this season.

He is a career 12-10 with a 4.13 ERA, 55 walks and 150 strikeouts in 213 1/3 innings over 71 games (29 starts) for the San Diego Padres (2024-25) and Royals (2025-present). The Padres traded Kolek and right-hander Ryan Bergert to the Royals for catcher Freddy Fermin on July 31, 2025.