Pittsburgh also announced Monday that it has purchased the contract of left-hander Mike Zagurski from Indianapolis, transferred right-hander Jeff Karstens from the 15-day to the 60-day DL and optioned right-hander Bryan Morris to Triple-A.
Karstens has been bothered by right shoulder inflammation.
Tabata, who is on the DL retroactive to Saturday, is hitting .272 this season.
Harrison broke up a no-hit bid by Detroit's Justin Verlander in the ninth inning last year. Verlander starts Monday against Pittsburgh, and Pirates manager Clint Hurdle joked that Harrison "can get a hit off Verlander" if needed.