"He looked like he had good velocity," Mud Hens manager Larry Parrish said. "He looked like he was healthy. As far as command-wise, he looked like he hadn't been out there in a while."
Rondon was scheduled to throw 20 to 25 pitches and was lifted after 22; 14 of those were strikes.
"You look at him throw, and the stuff is there," Parrish said. "It's a matter of locating."
Rondon battled to keep his fastball down, though it had enough life to remind fans of the power arsenal he displayed in Detroit two seasons ago before Tommy John surgery shut him down last season. His first pitch came in at 96 mph, but Blue Jays shortstop Jose Reyes -- who began his own rehab assignment on Thursday for Triple-A Buffalo -- lined it into left field for a single in his fourth and final at-bat.
Rondon induced three swings and misses, two on offspeed pitches, another on a riding fastball. That pitch went to Brad Glenn, who turned on a hanging slider on the next pitch for an RBI double.
"He threw some really good ones tonight," Parrish said.
As long as Rondon feels fine, he's scheduled to throw another 20 to 25 pitches for the Mud Hens on Sunday night, then follow the Hens on the road to Louisville, Indianapolis and Columbus. He's tentatively scheduled to throw back-to-back outings late next week, then pitch an extended outing of likely an inning-plus, for a total rehab assignment of around two weeks.
His return would be a major boost for a Tigers bullpen that could use a power strikeout arm, even if he doesn't necessarily assume a set role.
"You look at his arm and you think what he's capable of," Parrish said. "Guys that have that kind of arm, if you can throw strikes, you're pitching the eighth or ninth inning in the big leagues."
That was Rondon's career trajectory two years ago. The hope is to get him back on that path; his last Major League outing was in September 2013.
Jason Beck is a reporter for MLB.com. Read Beck's Blog, follow him on Twitter @beckjason and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.