PITTSBURGH -- Having sent Trevor Rosenthal back to St. Louis on Thursday for additional examination on his ailing right elbow, the Cardinals are awaiting word on the severity of an injury that has complicated what had been a settling bullpen.
Rosenthal threw eight pitches in Wednesday's 5-4 loss to the Red Sox before being pulled because of what he described as tightness in his pitching arm. On Thursday, the Cardinals placed Rosenthal on the disabled list and described the issue as irritation in the right elbow, around the area of the ulnar collateral ligament.
"I don't know what we're looking at," manager Mike Matheny said, when asked about the seriousness of the injury. "But, obviously, as well as he's been throwing the ball, losing him at all isn't necessarily something we're excited about."
The Cardinals have been cautious with their use of Rosenthal all year given the arm issues he's had over the last two seasons. Rosenthal missed nearly two months in 2016 due to rotator cuff inflammation, and twice in Spring Training he had to be shut down due to a strained right lat muscle. The second instance forced Rosenthal to start the season on the DL.
He recently alerted the Cardinals to soreness in his pitching arm, which is why Rosenthal had three days of rest before pitching on Wednesday. Upon entering, however, it was immediately evident that something was wrong. Rosenthal lacked command and velocity of his pitches.
"How he's been used this year has been a little bit based on how he feels," said John Mozeliak, Cardinals president of baseball operations. "But again, it's never been specific enough to where the medical staff has said, 'Let's go look at something.' But here we are, and obviously the drop in velocity last night, as we approached him on sending him back to St. Louis, at this point I think he realized that's probably the best decision."
Replacing Rosenthal on the roster is right-hander Luke Weaver, who provides the club versatility out of the 'pen. The Cardinals needed him immediately, too, as Weaver was summoned when Adam Wainwright's Thursday start lasted three innings. Weaver followed with two scoreless frames.

Weaver would be an option to slide into the rotation if the Cardinals need a spot starter, and the Cardinals are also willing to utilize him in shorter relief stints that are higher leverage.
"After we watched him pitch that last time out, [we] just realized he's one of the better arms we have," Matheny said. "To have him here in any capacity to fill any role, hopefully we don't need him to pitch long and then we can see how he fits in with the rest of the guys."
Filling the ninth-inning void will be more complicated. Rosenthal's re-emergence as closer helped stabilize a bullpen in disarray earlier this summer, and now the Cardinals are left to find another option. Mozeliak named Seunghwan Oh, who opened the season as closer, and Tyler Lyons as candidates to earn those opportunities. At least initially, matchups are likely to dictate who Matheny turns to on any given night.
"[There will be] opportunities for guys to step in and figure out how to get that inning put away for us," Matheny said. "Even when Trevor was the guy who was obviously going to get the ball, we kept everybody on point just in case. We'll probably stick with that for now."

Fantasy spin | Fred Zinkie (@FredZinkieMLB)
Only about three weeks into his latest tenure as the Cardinals' closer, Rosenthal is not necessarily a must-stash fantasy asset. Mixed-league owners who are dealing with additional injuries and don't have DL space to spare can likely afford to release the right-hander. With Rosenthal out, ninth-inning duties in St. Louis could return to Oh, who has logged a 0.82 ERA and a 0.91 WHIP across 11 innings since July 19. Oh should be added in most mixed leagues, though Rosenthal owners should first check waivers for widely available stoppers Arodys Vizcaino and Cam Bedrosian.