Harrison had a planned lumbar disk fusion in his lower back Tuesday. The team said the 28-year-old pitcher would be hospitalized at least two nights after the operation in Dallas by spine specialist Dr. Drew Dossett.
After winning 18 games in 2012 and then getting a $55 million, five-year contract, Harrison made only two starts last year before two operations on a herniated disk in his back. After four starts this season, he was diagnosed with significant nerve irritation and a forward displacement of his vertebrae, known risks after the earlier procedures.
Harrison is 49-33 with a 4.15 ERA while starting 100 of his 132 games, all with Texas since 2008.