Jimenez entered the season as the Tigers' No. 5 prospect, according to MLBPipeline.com, after racking up 30 saves in 2016 between Toledo, Double-A Erie and Class A Advanced Lakeland. He struck out 78 batters over 53 2/3 innings, while allowing just 26 hits and 17 walks.
Jimenez said he learned of his call-up with a 5 a.m. knock on his hotel room door. It was Mud Hens manager Mike Rojas delivering the news. Jimenez was on a flight from Indianapolis to Detroit shortly after that, but had a chance to call his father. Both of them were in tears.
"I still don't believe it," Jimenez said. "To be here with these guys, it's just amazing."
The 22-year-old right-hander made a further impression on Tigers officials in Spring Training before pitching for Puerto Rico in the World Baseball Classic. But Detroit's front office made it clear that it wanted Jimenez to get more time with Toledo to work on his secondary pitches before getting his big league opportunity.
This was an earlier call than expected, and certainly sooner than what the Tigers wanted. But Rondon's struggles forced an early decision, and Hens officials told Detroit manager Brad Ausmus and others that Jimenez was the best option.
"I think it's an imperfect situation," Ausmus said, "but we don't live in a perfect world."
Rondon came into this year with momentum after a strong finish to the 2016 season in the Tigers' bullpen, and he stepped into an eighth-inning role. But from the start of Spring Training, the hard-throwing 26-year-old was an enigma, from his fastball that wavered between his usual upper-90s heat and a lower-90s facsimile, to an offseason weight gain beyond his listed 275-pound frame.
Ausmus was hopeful that the start of the regular season would focus Rondon's efforts. But two disastrous eighth innings in three days indicated that wasn't happening, culminating in a squandered lead Sunday against the Red Sox.
Rondon allowed six runs on four hits and three walks -- one intentional -- while recording four outs over three outings. He has thrown 26 of 51 pitches for strikes, not counting the intentional walk.
"After a couple outings, it became apparent he wasn't ready," Ausmus said.
Left-hander Justin Wilson will serve as the Tigers' primary setup man in the eighth inning. For now, Detroit will pick and choose its spots with Jimenez, looking for lower-leverage situations.
"You might catch lightning in a bottle," Ausmus said. "But I caution you in thinking this is some kind of an answer. This is a young kid with a big arm who's still developing."