According to Mark Berman of Fox 26, Osuna has been told he needs Tommy John surgery to repair his elbow. The closer is reportedly seeking a second opinion.
Houston manager Dusty Baker confirmed Osuna was reviewing treatment options, telling reporters "it's not looking real good."
The recovery from Tommy John surgery typically takes between 12-15 months if there are no complications in the rehab process. For Osuna that would mean a return to the mound around October 2021 if the procedure is required. It's possible he could then help the Astros in a postseason run. Otherwise, Houston may not have its closer until 2022.
Since joining the club in 2018, Osuna has pitched 92 innings, earning 51 saves with a 2.45 ERA and 0.870 WHIP to go with 95 strikeouts on 15 walks.
It's another significant blow to an Astros pitching staff that's seen a number of crucial arms injured early in the season.
Reigning American League Cy Young winner Justin Verlander was shut down for a "couple of weeks" because of a forearm strain after his first start of the year in late July. It's possible he is able to return to the rotation, but the team has yet to give an update on his status.
Starters Chris Devenski, Jose Urquidy, Brad Peacock and reliever Joe Biagini are currently all on the 10-day injured list as well.
The Astros have so far been able to weather the issue at 5-4 and in second place in the AL West. Just how much longer the club can hold on—assuming the remaining pitchers stay healthy—may determine the fate of their season.