Right-hander Felipe Paulino flew back to Houston on Monday to be examined by team medical director David Lintner after complaining of soreness in his upper right arm.
"He told [head athletic trainer] Dave Labossiere he's had some discomfort for a while," general manager Ed Wade said. "I wish he had spoken up a little bit sooner, but we'll go ahead and get it addressed. ... Hopefully it's something minor."
Paulino wasn't a top candidate to make the rotation out of Spring Training, but he's considered to be one of the keys to the future of the pitching staff. Over two outings this spring, he yielded four runs over five innings. He also recently had an infection cut out of his right foot.
Wade hesitated to guess a diagnosis for Paulino's arm discomfort. He should receive a diagnosis from Dr. Lintner on Tuesday.
"[Labossiere] did his best to pin it down and just felt at this point it's vague enough for us to remain vague," Wade said.
The Astros also provided an update on Kaz Matsui, who flew to Houston on Sunday to have what was suspected to be a hemorrhoid problem examined. The most recent diagnosis is "anal fissure," and Matsui was due back to Kissimmee on Monday evening. He will hit and throw at the Astros' spring complex for four or five days and be re-evaluated at that time.
In other injury news, J.R. Towles is expected to miss three to five days with a strained right hamstring, and for at least the next two, he'll refrain from participating in on-field activities. He can catch bullpens but can't block balls in the dirt, and at this point he's limited to riding a stationary bike and walking on a treadmill.
"I can't run, but I can walk," Towles said.
Michael Bourn was kept out of the lineup on Sunday and again Monday because of mid-back spasms, but he's expected to play Tuesday.
Reggie Abercrombie is recovering rapidly from the flu, and Jose Valverde took Monday off to tend to a personal matter. He, too, will be back with the team Tuesday.
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.