"When I'm convinced that we have one," Leyland said, "we'll have a closer. Somebody will close games."
Rondon, ranked by MLB.com as the Tigers' No. 2 prospect, struck out the first two batters -- Oscar Taveras and Ty Wigginton -- swinging before throwing seven consecutive balls in his fifth-inning appearance.
Pitching coach Jeff Jones visited the mound to speak with Rondon, who proceeded to strike out Ronny Cedeno on a full count with Tony Cruz at first.
"He told me I was moving my body a little bit too fast and just to calm down a little bit," Rondon said through a translator.
"You can't get the third out before you throw a pitch," Leyland told Rondon upon his return to the dugout.
Two of Rondon's strikeouts came via his breaking ball, but fans cheered when the 22-year-old reached 100 mph on a fastball.
Christina De Nicola is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.