KANSAS CITY, Mo. — Astros ace Dallas Keuchel went back on the disabled list with neck discomfort and returned to Houston on Thursday to be examined.

Keuchel was scratched from Wednesday’s start against the Kansas City Royals with what the Astros initially said was an illness.

He is 9-0 with a 1.67 ERA in 11 starts for the Astros, who have the best record in the major leagues. The 2015 NL Cy Young Award winner is holding batters to a .183 average.

“He’s going on the DL for a minimum of 10 days,” Astros manager A.J. Hinch said. “That brings concern in its own right. Being symptomatic with the same injury from earlier in the year is concerning, but until we see him and talk with him, and get another report from the doctor, we just won’t know.

“I’m not sure what goes into these pinched nerves, or what the doctors’ plan will be to get him better. We need to get him right and back on the mound, we hope soon. If he misses one start, great. If it’s more than that then it is what it is.”

Keuchel was placed on the disabled retroactive to Monday. He was on the disabled list from May 15-May 26 with a pinched nerve in his neck.

He was activated May 27 and allowed one run and four hits over six innings to win at Texas. He struck out eight, walked two and threw 86 pitches.

“He was sick all the way through Arlington,” Hinch said. “He barely made it out to the bench a couple of days. He lost a little bit of weight and had taken some medicine to feel a little bit better. He threw when he got here to Kansas City, and was scheduled to start.”

He began warming up Wednesday for his start against the Royals, but stopped after a few pitches and returned to the clubhouse.

Houston selected the contract of right-hander Francis Martes from Triple-A Fresno. Martes, ranked as the Astros’ top prospect, is 0-2 with a 5.29 ERA in eight Pacific Coast League starts.

The Astros transferred right-hander Collin McHugh (elbow impingement) to the 60-day disabled list to make space on the 40-man roster for Martes.