The Astros are monitoring Tatsuya Imai after he reported arm fatigue following his third start; he was sent home for medical evaluation with hopes the issue is not serious.

Imai is undergoing tests in Houston to determine the cause of right-arm fatigue, as management weighs the quick turnaround from his recent start.

J.P. France was optioned to Triple-A Sugar Land, and Jayden Murray was recalled from the Space Cowboys; Murray carries a 1.50 ERA over six innings at Sugar Land.

In his latest outing, Imai retired only one out while yielding three runs on one hit, three walks and a hit-by-pitch over 37 pitches in a 9-6 loss to Seattle.

The situation underscores ongoing pitching depth concerns for the Astros amid injuries to several relievers and rotation options.

Houston has already placed right-hander Hunter Brown on the 15-day injured list with a right shoulder strain, and Cristian Javier followed with an IL stint for similar concerns.

Imai downplayed injury speculation, citing a tough mound at T-Mobile Park as a factor in his performance and noting he did not report an injury on Friday, though trainers were informed after media comments.

Imai is under a $54 million, three-year contract and currently owns a 1-0 record with a 7.27 ERA, with 11 walks and 13 strikeouts through 8 2/3 innings.