Herrera had allowed four earned runs in 1 2/3 innings, including an inning against the Sox on Friday, but after starting pitcher Shaun Marcum exited the game after the first inning with a left hip flexor strain, the Brewers needed a fresh arm in the bullpen.
"If Shaun hadn't gone down, we wouldn't be making this move," manager Ron Roenicke said. "But with Shaun going down early, we have to get a pitcher in here tomorrow with some length just to make sure that we're covered. We need a long guy that can give us two three innings."
Roenicke said the club hadn't decided yet who would replace Herrera.
Before Friday's game, Roenicke had nothing but good things to say about his 5-foot-6 reliever. Herrera is an inch shorter than Royals reliever Tim Collins, who was the shortest player in the Major Leagues on Opening Day.
- 131 wins
- 121 wins
"He's small," Roenicke said, laughing. "I mean, a lot of times with these guys it's a different look. It's like facing a guy that's 6-foot-10. He may only throw 90 mph, but it's a different look, and guys don't like it."
Herrera's arsenal includes a fastball, sinker, cutter and a screwball that he taught himself while in college at the University of New Mexico. He only recently learned the cutter, a pitch that has become increasingly popular among Major Leaguers, and throws it only on days when it feels good during pregame catch. But it's the screwball that allows him to get both right- and left-handed hitters out.
"In college, I had a terrible changeup, and I kind of turned it over and it was pronated until it pretty much spun like a curveball," said Herrera, demonstrating the way he throws his screwball, crossing his index finger on top of his thumb and keeping the ball in the back part of his hand. "It took a while to really hone in on throwing strikes and the command of it, but it's been my bread-and-butter pitch."
Jason Mastrodonato is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.