SEATTLE -- Arizona Diamondbacks ace Zac Gallen left his start against the Seattle Mariners on Friday night after feeling tightness in his right hamstring, but manager Torey Lovullo said he hopes Gallen won't miss any time.

Lovullo said after the D-backs' 6-1 loss to Seattle that Gallen felt a spasm in his hamstring and the decision to pull him was precautionary.

"Just a right hamstring spasm and I think we really dodged a bullet," Lovullo said. "Credit him. It's hard to pull back in those situations and understand what you body is feeling and call out your catcher. I think he's hopefully going to be fine. We're going to continue to evaluate him and no other signs of anything greater."

Gallen walked Mariners third baseman Josh Rojas leading off the sixth inning and then was removed by Lovullo in the middle of an at-bat against Julio Rodríguez. There was no obvious incident that caused an injury, but Galle appeared bothered and, after discussion with an athletic trainer on the mound, left the game.

Arizona trailed 2-1 when Gallen was removed and Seattle's lead ballooned to 6-1 after reliever Scott McGough gave up a grand slam to Mitch Haniger. Gallen was charged with three runs on three hits and threw 64 pitches.

Gallen had retired seven straight batters before walking Rojas. Lovullo said there were no immediate plans for Gallen to have any scans on his hamstring.

Gallen was 3-1 with a 3.00 ERA in his first five starts this season. He made 34 starts and went 13-7 with a 3.47 ERA last season, finishing third in the National League Cy Young Award voting.

While it doesn't appear to be serious, Gallen's issue is the latest ailment for the Diamondbacks' starting rotation. Arizona placed right-hander Merrill Kelly on the 15-day injured list earlier this week with a right shoulder strain. Right-hander Ryne Nelson was hit on the elbow by a line drive last week at San Francisco and isn't expected back until early May. And lefty Eduardo Rodriguez suffered a left lat strain during spring training, is currently on the 60-day injured list and is not expected to return until May or June.

Lovullo said it was hard not to have thoughts of the worst-case scenario while walking out to check on Gallen.

"I can't help myself. It's human nature with everything we've been going through over the past three, four weeks, plus," Lovullo said.