Karstens has been sidelined all year, including Spring Training, with inflammation in his pitching shoulder.
Karstens is now clearly out of the picture, but rehab continues for two other right-handers working their way back to the Pirates' depleted rotation:
• Charlie Morton's scheduled rehab start Saturday night, in which he is expected to throw 95 pitches for Triple-A Indianapolis, could be his last. It will have him in line to face the Giants on Thursday on regular rest.
• James McDonald, considerably farther away, gets his next turn Tuesday, when he is expected to throw six innings or 90 pitches for Indianapolis.
The Pirates announced they will call up top prospect Gerrit Cole to have him fill the other hole in the rotation and make his Major League debut Tuesday against San Francisco. It places Cole and McDonald on parallel pitching schedules, affording the Bucs flexibility for ensuing moves.
Injuries to Wandy Rodriguez (tight forearm) and Jeanmar Gomez (on the DL with forearm tightness) have left A.J. Burnett, Francisco Liriano and Jeff Locke as the tenured parts of a five-man rotation.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.