Herrera was part of the Dec. 21, 2007, trade that sent outfielder Josh Hamilton to the Rangers in exchange for starting pitcher Edinson Volquez.
"When you see him, he'll look like a batboy," Reds manager Dusty Baker joked. "I think it's a great story. It's a great thing for him to have made it like this. He'll be a motivation to a lot of people that said they don't have enough of this, don't have enough of that, too short, too tall, too skinny, too fat or too something. It's the beauty of baseball."
There has been nothing too short or too soft about Herrera's numbers.
In 26 games combined with Double-A Chattanooga and Louisville this season, Herrera was 3-1 with a 1.85 ERA. In 39 innings, he gave up eight earned runs, 26 hits and 11 walks with 26 strikeouts. Opponents batted .195 against him.
At Louisville, Herrera had a 1.27 ERA in 16 games with 16 strikeouts compared to four walks over 21 1/3 innings.
"It was very surprising. I didn't expect to get called up," Herrera said. "I've only had a month of Triple-A time and this is my second year of pro ball. I figured the organization would want a little more experience this early in the season. Thankfully, they were looking at how I'm throwing right now."
Herrera's Major League debut in the Reds' 3-2 loss to the Phillies on Tuesday night was pressure-filled but excellent. Called in to replace starter Aaron Harang in the seventh, there were runners on second and third with no outs and the heart of the Philadelphia lineup batting. Shane Victorino grounded out to the shortstop. After Chase Utley was intentionally walked, Ryan Howard struck out on an 80-mph slider. Pat Burrell was then called out on strikes looking at an 85-mph fastball, as Herrera escaped the jam.
"I was pretty nervous at first," Herrera said afterwards. "As soon as I threw the first pitch, it was like another outing -- just a bigger stage. I threw the ball well, hit some spots and getting them to chase. It was a great debut for me. I'm glad it's over though."
A native of Odessa, Texas, and an alum of Permian High School of "Friday Night Lights" fame, Herrera was selected by the Rangers out of the University of New Mexico his junior year after going 10-0 with 104 strikeouts. He joined the likes of Max Scherzer, Andrew Miller, Clayton Kershaw, Joba Chamberlain and Evan Longoria to make it to the Major Leaguers from the Draft class of 2006.
However, Herrera was taken 44 rounds after those guys. How did he move up so fast? Credit a batch of offspeed lefty stuff that keeps hitters off balance, similar to Jamie Moyer or Tommy John later in his career. Herrera is also one of the few pitchers around that still uses a screwball effectively.
"It's definitely my money pitch," Herrera said. "I throw a lot of different pitches. I learned it my sophomore year of college. I just kind of self-taught. It's developed over three years with trial and error and grips to where it's gotten now."
"To be successful in this game, you have to throw over the speed limit or under the speed limit," Baker said. "Guys that throw under the speed limit usually don't get the same opportunities as those who throw over the speed limit."
As Herrera talked to reporters in the clubhouse tunnel, reliever David Weathers walked by.
"[He's] the only player you get to look down to," Weathers said.
Herrera has heard all the short jokes and can take it, especially now that he's in the big leagues.
"I heard that a lot early in my career and at the beginning of college," Herrera said. "As far as making it, no one has said, 'You're too small to make it.' I mostly just get picked on a little bit more for being the small one of the group."
Mercker was previously on the DL from May 9-23 because of the same injury. He has returned to Cincinnati to be examined. He was 1-0 with a 3.29 ERA in 15 games. Since returning, he threw two scoreless innings, including one for a victory on May 30 vs. the Braves.