"He feels fine, he feels healthy," Ausmus said. "He just feels inconsistent with his mechanics."
Considering Zimmermann's previous simulated game prompted a repeat simulated game rather than a return to the Tigers' rotation, the next step is unclear. Ausmus said he needed to talk with pitching coach Rich Dubee before determining the next step in the next day or two.
Zimmermann, who wasn't available for comment afterward, has made two outings for the Tigers since the end of June, spending two different stints on the disabled list with what the Tigers labeled a right neck strain. He gave up six runs on four hits, three of them home runs, over 10 batters against the Orioles on Sept. 10, prompting the simulated games.
With Zimmermann on simulated game duty and both Anibal Sanchez and Mike Pelfrey dealing with their own pitching struggles, Buck Farmer will start Wednesday night against the Twins. It'll be Farmer's first start in the big leagues since Aug. 29, 2015.
With Farmer starting, Sanchez and Pelfrey are both in the Tigers' bullpen for now, Ausmus said, though they could make a spot start if needed.
Castellanos still dealing with sore hand
Nick Castellanos' second test in the past week against live pitching went about the same as the first. He faced instructional league pitching on Monday in Lakeland, Fla., Ausmus said, but again suffered lingering soreness in his previously fractured left hand.
"He hit live and still felt it on some swings," Ausmus said, "so today he just took [batting practice]."
Castellanos will remain in Lakeland until the Tigers return home on Friday, Ausmus said. "But I would say it's going to be a little longer [before he's ready]."
Castellanos broke his hand on a hit-by-pitch in early August.
Ausmus said Castellanos can't do any damage to his hand swinging, so he'll keep working out in hopes of returning. Still, Ausmus said, "It's getting more unlikely with every passing day."
Tigers renew affiliation with Triple-A Toledo
The Tigers will continue their affiliation with the Toledo Mud Hens for at least another two seasons. The two clubs on Tuesday announced a extension of their player-development agreement through 2018.
The Mud Hens have been the Tigers' Triple-A affiliate since 1987, winning the International League's Governors' Cup championship in 2005 and '06. The close proximity, about an hour's drive, makes it one of the most envied relationships in baseball, allowing the Tigers the advantage of calling up players on short notice on DL moves and sending players on rehab assignment while allowing them to drive back and forth from Detroit if they wish. Thirty players wore both Mud Hens and Tigers uniforms this season.
"Toledo runs a first-class operation and continues to play an integral role in preparing our players for the Major Leagues," Tigers vice president of player development Dave Littlefield said in a statement. "Our organizational goal is to field a competitive and winning team in Toledo, and we certainly would like to reward Mud Hens fans with a championship to celebrate."