The right-hander began a rehab assignment in Triple-A on June 21 and remained in Memphis when he was taken off the disabled list. In 11 appearances, Salas allowed seven hits and four runs (one earned) in 11 2/3 innings. He struck out 11 and only just one. He recorded a save in four of his last five appearances.
"I feel good," Salas said on Thursday. "I feel different, because there is no pain and I'm more relaxed. I feel different. I am more confident in my pitches. There is no pain, so I can be more aggressive in the zone."
With Salas set to be added, the Cardinals will enter this weekend series with eight relievers. The Cardinals have the extra arm in the 'pen since they won't need a fifth starter until later this month.
As for sending out Butler, who allowed five hits and three earned runs in 13 2/3 innings during his big league stay, the Cardinals' biggest motivating factor was needing to find a way for him to pitch regularly. Butler had pitched just twice since June 25.
"It just wasn't fair to him," manager Mike Matheny said. "We could barely get him in. If we thought he was a player who wasn't going to be around the league for a while, it wouldn't have been as big of a deal. We think he can be a very good pitcher, and he was not improving by how we were using him."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.