The Pirates have placed starter Charlie Morton on the 15-day disabled list because of shoulder fatigue.
Reliever Steven Jackson had his contract purchased from Class AAA Indianapolis.
General manager Neal Huntington said in a statement: "Charlie has been battling mild shoulder discomfort and fatigue off and on for the majority of the season. Charlie has not wanted to use it as an excuse and has worked to pitch through it. Until now, we felt we could work through the issue without risking additional damage. We now feel that the best way to get Charlie back on track is to give his shoulder appropriate rest and recovery time to allow him to get back to 100 percent."
The Pirates' starter for Tuesday now is officially TBA.
Morton's nine losses -- an 8-2 defeat in Cincinnati Thursday night left him with a 1-9 record to date -- and 9.35 ERA were the worst in the majors.
Morton is scheduled to head to Pirate City on Saturday to begin his rehabilitation, which, manager John Russell said, is scheduled to include a rehabilitation start or two in the minor leagues before Morton returns to major-league duty.
"I think he's been trying so hard, he's been working so hard, he's been working so hard on the side, his shoulder's just tired," Russell said. Morton threw one pitch in the first inning Thursday measured at 94 mph, then was able to reach 94-95 against Scott Rolen, Johnny Gomes and Drew Stubbs in the second -- a range more the norm for him. "That's why he's going to Florida, part of it: To rehab, but also to kind of get out of this environment, to kind of regroup. So it will be good for him. again, he's worked really hard. I think the physical and mental drain of trying to piece it together -- I think it'll be good for him to get away from this atmosphere while he's rehabbing to try to relax and try to get a litle bit fresher outlook on things."