gettyimages 691712808 Astros Keuchel On 10 Day Disabled List With Neck Discomfort

ARLINGTON, TX – JUNE 2: Dallas Keuchel #60 of the Houston Astros delivers against the Texas Rangers during the first inning at Globe Life Park in Arlington on June 2, 2017 in Arlington, Texas. (Photo by Ron Jenkins/Getty Images)

KANSAS CITY, Mo. (AP) — Astros ace Dallas Keuchel is going 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 baseball. The 2015 National League Cy Young Award winner is holding batters to a .183 average.

Keuchel was placed on the disabled Thursday 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 on four hits over six innings to win at Texas. He struck out eight, walked two and threw 86 pitches.

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

The Astros purchased the contract of right-hander Francis Martes from Triple-A Fresno to fill Keuchel’s roster spot. 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) from the 10-day to the 60-day disabled list to make space on the 40-man roster for Martes.