ST. LOUIS -- Bothered once again by a right shoulder impingement, veteran reliever Luke Gregerson returned to the disabled list on Monday and will now huddle with the organization's medical staff to determine a new course of action to address the recurring injury.
Neither Gregerson, nor interim manager Mike Shildt, could say with any certainty that the right-hander would return to the mound this season.
"I don't know long term exactly," Gregerson said. "I would say, ultimately, we just need to find a way to get back to where we were before and to get ahead of it. It's not for a lack of effort, a lack of stuff in the training or weight room. I've done everything possible to make sure it didn't come back, and, unfortunately, it did. Hopefully, moving forward, we can gameplan for that."
In the first season of a two-year, $11-million contract he signed back in December, Gregerson has seen little time on the field. He rehabbed from hamate surgery over the winter, sustained a hamstring injury in spring that kept him off the Opening Day roster and has twice been sidelined by a shoulder issue. During his last stint on the DL, Gregerson also underwent right knee surgery.
He appeared in five games this month, but gradually felt discomfort in his shoulder return.
"It's a little concerning when he's not able to go out and play catch and feel comfortable," Shildt said of Gregerson, who has a 7.11 ERA in 17 appearances. "He's a great competitor, really disappointed and is trying to fight like crazy to get through it. It's not fair to us to ask him to compete in that scenario right now."
Moving Gregerson to the DL opened up a roster spot for lefty Chasen Shreve, who the Cardinals acquired in a trade with the Yankees late Saturday. Shreve had never been to St. Louis before arriving on Monday.

"It's a big change," said Shreve, who had a 4.26 ERA in 40 appearances with the Yankees. "I'm glad to be here."
Also on Monday, the Cardinals optioned reliever Tyler Webb to Triple-A Memphis and activated Carlos Martinez from the disabled list. Martinez will start the club's series opener against the Rockies. Webb made his Cardinals debut with a scoreless, two-inning performance on Sunday.
Minor matters
• The Pacific Coast League named Adolis Garcia its Player of the Week after the Memphis outfielder hit .414 with six homers, nine runs scored and 14 RBIs in six games. Garcia tied franchise records with three home runs and eight RBIs last Thursday alone. He is the first Memphis position player to earn the weekly honor this season.
• Three other players in the organization also netted weekly honors from their respective leagues. Andy Young (Double-A Springfield, Texas League) and Yariel Gonzalez (Class A Peoria, Midwest League) were selected as Players of the Week. Michael Baird earned New York-Penn League Pitcher of the Week recognition.
• Playing in his first game since being promoted to Triple-A Memphis, outfielder Lane Thomas tallied three hits, including a double and triple, on Sunday. He also scored twice and drove in two. The Cardinals acquired Thomas from Toronto for international bonus pool money last July.