The Kansas City Royals placed ace right-hander Seth Lugo on the 15-day injured list Thursday due to a lower back strain.

The move is retroactive to Monday.

Lugo, 35, was initially listed to start Thursday's game against the Los Angeles Angels before being pushed back two days. Then he was evaluated further Thursday and was placed on the IL.

The 2024 All-Star has struggled of late. He had a 3.06 ERA after his start on Aug. 3 and has been racked in four of his ensuing five starts, going 0-2 with a 10.23 ERA.

Lugo's ERA now sits at 4.15 to go with an 8-7 record.

Meanwhile, the Royals are hoping to get another 2024 All-Star back soon in left-hander Cole Ragans (2-3, 5.18). He has been on the IL for nearly three months with a strained left rotator cuff.

Ragans, 27, pitched batting practice Wednesday and manager Matt Quatraro was impressed.

"He looked good," Quatraro told reporters. "He was healthy and threw the ball free and easy. He got to face hitters -- amped up the adrenaline a little bit -- and so far so good. ... Everything was positive."

Lugo finished second in the American League Cy Young Award balloting last season. Ragans placed fourth.

The Royals promoted right-hander Stephen Kolek from Triple-A Omaha on Thursday and he might end up being the Saturday starter.

Kolek, 28, was acquired at the trade deadline from the San Diego Padres and was sharp in his lone start for Kansas City, allowing one run and four hits in six innings in a no-decision against the Detroit Tigers last Saturday.

Counting his time with San Diego, Kolek is 4-5 with a 3.99 ERA in 15 starts this season.

Left-hander Noah Cameron (7-6, 2.92) was set to start Thursday's game against the Angels.