ST. LOUIS -- With Michael Wacha (right shoulder stress reaction) and Trevor Rosenthal (right shoulder inflammation) having both begun mound work in recent days, the Cardinals may be only about a week away from enhancing their bullpen depth.
On Wednesday, Wacha threw his first bullpen session since being shut down on Aug. 9 due to a recurring injury within his right scapula. He threw 25 pitches in the session at moderate intensity and said he was particularly relieved by how much more extension he was able to get on his finish than he had just prior to going on the disabled list.
"I'm real happy with where I'm at," said Wacha, who was 7-7 with a 4.45 ERA in 23 starts before the injury. "It's a great feeling. I'll just keep going forward and see where it goes."
With fewer than four weeks remaining in the regular season, the Cardinals believe Wacha's best fit will be out of the bullpen. Wacha can return quicker that way given that he won't have to build up as much arm strength. Manager Mike Matheny indicated that Wacha may be ready to test his pitches against hitters as early as this weekend in a live batting practice session.
Rosenthal, who has thrown two bullpen sessions this week, is in the same spot. The Cardinals have tentatively planned his next step to be live BP on Saturday. Rosenthal said earlier this week that he is eyeing a return around the middle of next week, assuming he incurs no setbacks.
"I'd love to have Trevor in the 'pen when he's feeling good and he's right, and an opportunity to get Michael involved, too," Matheny said. "We love to keep pushing them and knowing that when they get back, we'll figure out how to get them involved. Especially with where our club is right now, we could use some experienced help in the bullpen."

Though the Cardinals already have an 11-man bullpen, Matheny would like a few more late-inning options to emerge. That could help with workload concerns surrounding Matt Bowman, Zach Duke and Seunghwan Oh.
In other injury news, Aledmys Díaz (right thumb fracture) played a full game at shortstop on Wednesday as part of a rehab assignment with Double-A Springfield. He went 0-for-4 with a sacrifice fly. General manager John Mozeliak said the Cardinals have not ruled out a weekend return for Diaz, who has been out since July 31.
Matt Holliday (right thumb fracture) grabbed a bat on Thursday for the first time since having thumb surgery on Aug. 17. He plans to take dry swings and play catch this week as part of a rehab plan that could have him back for the final week of the regular season. His biggest challenge will be getting the timing of his swing back within such a limited time.
Worth noting
• The Cooperstown Baseball Hall of Fame Tour will remain open in the Ballpark Village parking lot through Sunday, and any fan who shows a 2016 Cardinals ticket can receive a discounted ticket ($10) for the traveling exhibit.
• The Cardinals will hold an afternoon ceremony on Friday to announce the distribution of over $175,000 through their grant program to 81 area nonprofit groups that support children.