If he can, he could put heat on the left-handers currently in the Phillies bullpen: Antonio Bastardo, Jeremy Horst and Joe Savery. The Phillies optioned right-hander Tyler Cloyd to Triple-A Lehigh Valley on Thursday as left-hander John Lannan will take his place in the rotation Monday against the Nationals. The Phillies recalled Diekman to take Cloyd's place, although he will not join the team until Friday in Colorado.
If Diekman shows something this weekend at Coors Field, maybe he remains as a lefty specialist and the Phillies option Horst or Savery to Triple-A on Monday, when they need to activate Lannan for his start at Citizens Bank Park.
"Anybody on our team that shows a good outing, they can stay on our team," Phillies manager Charlie Manuel said. "It depends on how he looks and how he throws. Everyone down there, they have a chance."
Diekman's overall numbers in Triple-A are not good -- 24 walks in 30 innings and a 5.70 ERA in 30 appearances -- but he has been fantastic against left-handed hitters. They are hitting just .161 with a .461 OPS against him with just five hits and two walks in 34 plate appearances.
It is no secret the Phillies bullpen has been a major problem this season, and the team's left-handers have played a significant role in those struggles. Bastardo, who is the bullpen's top lefty, has struggled in tight spots. He allowed the game-winning run to score Tuesday and put the game-tying and game-winning runs on base Wednesday. He allowed big hits against left-handed hitters each time. Lefties are hitting .263 with an .823 OPS against him.
Lefties are hitting .282 with an .832 OPS against Horst, who is second on the team in appearances despite a 5.55 ERA. Savery has pitched just three times with the Phillies, although lefties are 3-for-4 against him.
"I think Bastardo is that guy," said Manuel, when asked about a left-handed specialist. "Every now and then we run him through right-handers because we have to, because that's who we have that night. But, really somewhere down the line, when they come into the game now, they have to hold and lead and that's what we're not getting."
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.