Lambo was placed on the 15-day disabled list on May 6. His rehabilitation took him to the club's Minor League facility in Bradenton, Fla., where he is able to take part in "pretty limited activity," general manager Neal Huntington said on Sunday.
"He still feels it in daily life. He still feels it as we try to push through," Huntington said. "We're trying to keep the baseball activities going as best we can."
Lambo, the Pirates' No. 19 prospect, made three starts and saw most of his plate appearances as a pinch-hitter. He was the Pirates' only left-handed bat off the bench to begin the season.