Hart underwent season-ending surgery on his right shoulder last May and was initially expected to be ready for the start of the 2011 season. But inflammation in that shoulder forced Hart to shut down just before the start of Spring Training and he has only thrown three light bullpen sessions so far.
That progression means Hart is about two months behind the rest of the pitchers. He can make up that time by throwing in extended Spring Training once the regular season begins.
"He's not suffered a setback," general manager Neal Huntington said. "It's just taking a little bit longer than maybe the quick returns take. But the 12-month window is still a very realistic window."
Hart was preparing to enter the season out of options, though the Pirates will now have more time to determine whether or not the right-hander is still a part of the organization's future. He hasn't pitched in the Majors since 2009, when he went 1-8 with a 6.92 ERA in 10 starts after being acquired by the Pirates.
Hart will be eligible to come off the disabled list 60 days after Opening Day.