Before following through with the surgical procedure, Hart will receive a second opinion from Dr. James Andrews in Birmingham, Ala., next week. Pirates general manager Neal Huntington will not comment on the injury until after that visit takes place.
Friday's news came as a surprise to Hart, who believed that he was simply being bothered by biceps tendinitis. That said, the right-hander revealed on Friday that his arm hadn't been feeling exactly right for a while now.
"I think it's something that I've been dealing with since Spring Training," Hart said when reached by phone. "You try to pitch through it and hope it goes away. Something had not felt quite right this whole season, but I got to a point in the last week or so when it had progressed into what I thought was biceps tendinitis."
Hart's most recent start for Triple-A Indianapolis came on Wednesday. He lasted two innings, giving up seven earned runs on seven hits and four walks to Pawtucket (R.I.). He was placed on the disabled list the next day.
Hart's injury is another hit to the organization's starting pitching depth. The Pirates have already had to tap into their Triple-A rotation three times this month, and Hart was seen as the next callup candidate.
Furthermore, the injury makes the Pirates' July 2009 trade with the Cubs look that much more one-sided, in favor of Chicago. Pittsburgh acquired Hart, right-hander Jose Ascanio and infielder Josh Harrison at the Trade Deadline last year in exchange for veteran reliever John Grabow and starter Tom Gorzelanny.
Ascanio made just two appearances for Pittsburgh last season before undergoing right shoulder surgery in October. He's not expected to return to the mound until June at the earliest. Now Hart, who went 1-8 with a 6.92 ERA in 10 starts for the Pirates last year, is dealing with a lengthy recovery of his own.
Even if the odds may be against him, that's not to say, of course, that Hart can't still come back and prove to be a valuable acquisition in the future.
"I think this gives me an opportunity to get 100 percent healthy and then focus on the pitching aspect of it and get back on the mound and really show everyone that you haven't heard the last of me yet," Hart said. "This isn't the end."
It had already been a trying few months for the right-hander, who came into Spring Training the favorite to win the fifth starter job. However, Hart struggled immensely with his control all spring and found himself beginning the year in Indianapolis' rotation as a result.
Hart's results with Indianapolis were mixed, though efficiency and command were issues throughout the month. In five appearances, Hart allowed 13 earned runs on 18 hits in 17 1/3 innings. He walked 11 and struck out 19.
For Hart, this diagnosis at least provided an explanation as to why his side work never translated into game results.
"This is a year where I've worked harder than I've worked in my entire life," he said. "I put in more hours this offseason than I've ever put into an offseason in my life. So the frustration was mounting day by day when you start not getting the results. There's a reason why I was going out there and throwing 60 pitches in the bullpen and working really hard in between games mechanically and then going out there and not being able to repeat the simple things. For me, it gives me a little bit of an explanation."
With Hart out indefinitely, the Pirates have promoted right-hander Michael Crotta to Triple-A, where he will step into Hart's spot in the rotation. In four starts with Double-A Altoona this year, Crotta was 2-0 with a 1.78 ERA. He had walked just three and struck out 16 in 25 1/3 innings.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.