Jeff Karstens will miss at least 10-12 following surgery. (USATSI)
Jeff Karstens will miss at least 10-12 weeks following surgery. (USATSI)

More MLB: Scoreboard | Standings | Probable Pitchers | Sortable Stats | Odds

The Pirates have been without right-hander Jeff Karstens all season because of right shoulder inflammation, but he appeared to be on his way back after making a pair of minor-league rehab starts last month. Instead, he had to be shut down with discomfort two weeks ago. On Friday, he had surgery:

The full extent of the injury is unknown, but the 10-12 week recovery time suggests it may not have been a significant tear. The team has not released any further details, however.

Karstens, 30, went 5-4 with a 3.97 ERA and 1.15 WHIP in 90 2/3 innings spread across 15 starts and four relief appearances last season while battling hip issues. He went 9-9 with a 3.38 ERA in 162 1/3 innings back in 2011.

Pittsburgh re-signed Karstens to a one-year, $2.5-million contract in January after non-tendering him in November.