ST. LOUIS -- After playing in three games as part of a rehab assignment with Double-A Springfield, outfielder Tyler O'Neill returned to St. Louis on Friday and was activated from the injured list prior to the Cardinals’ series opener against the Reds. The club optioned Lane Thomas back to Triple-A Memphis to create roster space for O’Neill.

O’Neill, who missed eight games while healing from an ulnar nerve subluxation in his right elbow, finished 1-for-11 with a home run during his stint in Springfield. He was not tested much defensively, but he did not feel any limitations with his arm strength while throwing on the side.

“It was nice to get into a groove, get some at-bats together, get my rhythm back,” O’Neill said. “I obviously needed that after a week or so off. I’m feeling good. I just want to carry that over here.”

How much playing time awaits O’Neill isn’t so certain, especially since the Cardinals already are trying to work four others -- Marcell Ozuna, Dexter Fowler, Jose Martinez and Harrison Bader -- into three outfield spots. O’Neill has started four games this season and is 1-for-4 as a pinch-hitter.

“We’ve got a talented group of outfielders,” manager Mike Shildt said. “We know that. We’re appreciative of the depth we have. The opportunity today presents itself for the guys who are in the lineup, and the other guys will be ready to come off the bench and help accordingly.”

Rehab roundup

• Michael Wacha (left knee patellar tendinitis) returned to the mound on Friday and threw a pain-free bullpen session at Busch Stadium. He is on track to come off the injured list and start against the Nationals on Monday, though Shildt said the club would wait to make sure Wacha recovered well from Friday’s work before making that assignment official.

• Carlos Martínez (right shoulder cuff strain) also had a bullpen session scheduled for Friday. While the Cardinals have already decided to have Martinez work toward a return as a reliever, Martinez is expected to huddle with the medical staff and front office members this weekend to more specifically outline his next rehab steps.

• Luke Gregerson (right shoulder impingement) pitched a scoreless inning for Springfield on Wednesday as part of his continuing rehab assignment. It marked the eighth consecutive scoreless appearance by Gregerson, who is slated to come off the injured list while the team is on the road next week.