"It went very well; he was very happy," head athletic trainer Kevin Rand said. "At the end, he shortened up and let some balls go nice and easy and felt very good, very encouraged."
While he's felt good physically, throwing fastballs and changeups, he's struggled to throw sliders without soreness. According to Brooks Baseball, Rondon has thrown his slider on about 22 percent of his pitches.
Rondon will play catch again on Thursday and try to throw fastballs and changeups at normal distance from flat ground. The Tigers are hopeful he will be able to throw a bullpen with his slider by the end of the week.
"Obviously we've taken a cautious approach, because he's a young guy," Rand said. "He was throwing fastballs and changeups fine, but he was feeling it when he was spinning his breaking ball a little bit, so we wanted to make sure that we had nothing go on. We checked him out, but we just ended up giving him some time."
Bobby Nightengale is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.