Chen was banged around in his last two starts of his Minor League injury rehabilitation assignment. The good news is the bulging disc that put him on the disabled list in early May has healed.
"Right now, the back feels great. I'm very happy with the way the workload is going," Chen said. "I've been doing more stuff. Yesterday was the first day I ran outside and it feels good. So I feel like I'm progressing nicely."
Manager Ned Yost isn't too concerned about the hits and runs that Chen has been giving up.
"What did I tell you in the spring?" Yost asked. "He's not a Spring Training pitcher. Probably not a rehab pitcher either."
Depending on how third baseman Danny Valencia reacts to batting practice swings on Monday, he's likely to begin a rehab assignment with Omaha as well. He's been out since June 1 with a left hand strain.