Casparius (shoulder) experienced arm fatigue while on a minor-league rehab assignment and has been shut down from throwing, MLB.com reports.
Casparius landed on the injured list in mid-April due to right shoulder inflammation. He began a rehab stint July 25 and has logged 10 appearances with Triple-A Oklahoma City. The righty reliever struggled to a 7.27 ERA, 2.56 WHIP and 10:14 K:BB over 8.2 innings during his rehab assignment, though he had been showing improvement with just one earned run allowed across his past five frames. It's unclear how much Casparius' arm fatigue will set him back, but it's certainly possible that he won't return to the big-league club this year.