Lannan allowed six earned runs on eight hits in 12/3 innings against the Reds after pitching well in his first two starts, when he had a 2.77 ERA.
The lefthander said that he had experienced knee soreness before but that it would then go away. This time was different. Lannan said he felt pain when he pitched to the second batter of the game, Zack Cozart.
"That change-up to Cozart, I realized something was up," Lannan said. "I couldn't push off and get the ball down in the zone."
The Phillies will need someone to replace Lannan on Monday against visiting Pittsburgh, and it's likely that Lehigh Valley lefthander Adam Morgan will be bypassed this time. Morgan pitched five innings Thursday against Pawtucket and would be throwing on short rest if he came back Monday.
"I am not sure we want to bring a kid back on short rest," general manager Ruben Amaro Jr. said. "It probably doesn't make sense."
The Phillies will recall reliever Joe Savery from Lehigh Valley on Friday. Amaro said the team will bring up a starter on Monday to pitch in Lannan’s slot. He said IronPigs pitchers Tyler Cloyd, Jonathan Pettibone, and Ethan Martin are possibilities.
Like Manuel, Amaro said that Lannan could be out for some time.
"It's a fairly serious injury," Amaro said. "One of the things we want to be cautious about is pushing it and having him rupture it."
Brown feeling better
Domonic Brown seemed relieved. Like Lannan, Brown was hurt Wednesday night. He injured his back when he dove for a ball in the first inning.
Brown said he was feeling much better Thursday. He was diagnosed with a back strain.
"I feel like I am ready to go," Brown said before the game. "I took a lot of swings in the cage and I felt pretty good."
Brown said he hoped to play on Friday, but Manuel wouldn't say whether Brown would return to the lineup then.
Amaro said rightfielder Delmon Young, recovering from offseason microfracture ankle surgery, continues to progress in extended spring training.
Amaro said that starting Thursday, Young was expected to play three straight seven-inning games in the outfield and then the Phillies would decide when he would go on a rehab assignment.
"He's not ready to be here yet," Amaro said.
Contact Marc Narducci at firstname.lastname@example.org. Follow @sjnard on Twitter.