KANSAS CITY, Mo. -- Royals ace Cole Ragans will undergo testing on his left groin after the All-Star left-hander was forced to leave Thursday's start against the Colorado Rockies after just three innings and 62 pitches.

Ragans had allowed four runs on three hits -- two of them homers -- and two walks before Angel Zerpa replaced him for the fourth inning of a 7-3 victory over the Rockies.

Manager Matt Quatraro said Ragans had trouble getting loose before the game and his groin began to bother him as the innings went on.

"As he was sitting there between innings, between the third and fourth, it tightened up on him," said Quatraro, who thinks some of Ragans' command problems were related to the groin issue.

"I did not talk to him yet, but I would assume, you know, if he's not comfortable pushing off, you're seeing him cut some stuff off, which makes sense, based on most of those misses. Just probably wasn't getting through it."

Ragans went 11-9 with a 3.14 ERA and led the league in strikeouts per nine innings during a breakout season last year. He is 1-1 with a 4.40 ERA in six starts this season, including a dismal outing last week against the Tigers.

"Cole was not 100%," catcher Salvador Perez said Thursday. "I could tell from the bullpen he was not right."

The bullpen picked Ragans up, though, tossing six scoreless innings in relief. Zerpa and Steven Cruz tossed two apiece, Lucas Erceg cruised through the eighth and Carlos Estevez handled the ninth to earn his sixth save.

In other injury news, Quatraro said right-hander Alec Marsh would begin a new throwing progression Friday after he was shut down a few weeks ago with more soreness in his right shoulder. The Royals hope to have him back sometime in June.

Speedy outfielder Dairon Blanco also is on the mend after dealing with a right Achilles injury. He went through a full workout on Tuesday, and Quatraro said it's possible that Blanco could be headed on a rehab assignment soon.

"That was a huge step forward. He had a ton of volume out there," Quatraro said. "We've got to get through this weekend, but if everything goes smoothly, we'll get him out sometime next week."