"It's good. We haven't had him for, it seems like, a long time," manager Joe Girardi said. "It's good to have him back. We're encouraged."
Robertson was reinstated to active duty on Thursday, as the Yankees optioned right-hander David Phelps to Class A Tampa in order to get stretched out as a starting pitcher following a stint in long relief. Girardi said that Phelps took the demotion in stride.
"He was good. He understood," Girardi said. "It's never a fun time to listen to that conversation, but this is a young man that we have high hopes for. We think he's going to be a starter for us in the future.
"Our starters have been giving us a lot of distance, so he's going to go down and start. They're building him up down in Tampa, and then he'll go to Triple-A. If we need him before that, we'll call him back."
Robertson made two appearances while on a Minor League rehab assignment for a strained left oblique, last pitching a scoreless inning with a strikeout on Tuesday. He last appeared in the Majors on May 11.