"It was really more that Krol was pitching well more than anything else," Ausmus said before his club posted a 4-0 victory over Cleveland.
In a corresponding move, the Tigers optioned starter Shane Greene to Toledo. Lefty Kyle Ryan will start on Tuesday for Detroit.
• Struggling Greene optioned to Triple-A
Since being optioned on April 22, Krol says he has worked extensively with Toledo pitching coach Mike Maroth to improve his pickoff move and command of offspeed pitches.
One of the biggest improvements he pinpointed was the development of his curveball into an out pitch.
"Earlier in the year, my offspeed wouldn't really be close to the zone," Krol said. "Now it's closer to the zone. I'm getting swings on them."
Ausmus also mentioned improvements the lefty has made to his cutter, a pitch which he began implementing in Spring Training.
"It came to him pretty quickly," Ausmus said. "He started throwing it, and it immediately showed signs of being a potentially very effective pitch."
Krol compiled a 4.76 ERA in six games with the Tigers between April 8-22. On April 21, he yielded a pair of home runs to the Yankees. but he didn't allow any with the Mud Hens, an encouraging sign for the lefty.
"He seems like he's in a good spot, so hopefully he helps us here," Ausmus said.
• Catcher Alex Avila, whose recovery from a loose body in his left knee was briefly shut down last weekend because of soreness, was cleared to resume baseball activities on Wednesday. Ausmus said Friday the setback was very minor.
"Just a few days," he said. "It's three days, maybe four days. He's hitting again today."
• Victor Martinez continues to look good taking batting practice, Ausmus said. The designated hitter was placed on the disabled list on May 19 with inflammation in his surgically repaired left knee.
"There's definitely a rehab [assignment] down the road," Ausmus said. "It's just how long the road is."
• Reliever Bruce Rondon, who is rehabbing from Tommy John surgery, will pitch for the Mud Hens on Friday night in Pawtucket. He was expected to join the Tigers earlier this month, but he has been hit hard in Triple-A, struggling to a 12.15 ERA in seven appearances.