Leyland noticed something in Zumaya's mechanics on Friday night and although the Tigers' medical staff did not find anything serious after the game, the club will continue to err on the cautious side.
"Seems like he gets to a certain point where he doesn't finish pitches," Leyland said.
The hard-throwing Zumaya left the game on July 27 with tightness in his right triceps, and cited throwing too many curveballs as part of the problem.
Zumaya worked through the initial tightness and was slotted back into the 'pen on Tuesday, as the Tigers didn't expect the minor condition to linger.
Unfortunately, Friday's outing brought back the same familiar tightness, although it is now slightly above Zumaya's triceps. The right-hander reported no problems throwing any breaking balls and only felt tightness on a portion of the fastballs he threw to six Rays batters.
The Tigers' bullpen has already been a sore spot for the club this season.
Zumaya was sidelined for the first 2 1/2 months following a rare surgery last fall to repair the A/C joint in his shoulder, while Fernando Rodney has been a victim to a high pitch count since his return from the disabled list (right shoulder tendinitis) on June 16.
Upon dealing for reliever Kyle Farnsworth on Wednesday, Leyland was hopeful that the club had "struck lightning in a bottle" and could interchange the trio of arms for the game's final innings.
But Zumaya's setback has thrown another wrench into a season littered with pitching disappointments.
Detroit has also been without expected starters Dontrelle Willis and Jeremy Bonderman for most of the season and has scrambled to find arms to pick up the slack in the game's front-half.
"It hasn't been an ideal situation all year," Leyland said. "When you have to fight through the pitching problems you normally have problems. ... That usually mean you are struggling, you are fighting your [butt] off to survive. And I think we're doing it, but we're working pretty hard."
Even with Detroit's pitching woes, the Tigers still remain in the American League Wild Card race, and having Zumaya and Rodney return to form would be a big boost.
"I think if you could pitch them and everything is right, then I think by September, you might have them normal," Leyland said. "But [so far] you haven't been able to do that."
Zumaya is scheduled to be evaluated by the team's medical staff again on Saturday and assuming he comes through clean, the Tigers hope to have him available for Tuesday's series opener against the White Sox.
Brittany Ghiroli is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.