Ray Searage believes A.J. Burnett is likely to retire, according to 93.7 The Fan's Ben Livingston (via Matt Bandi).
"Right now I'm leaning that way, where he's going to retire."
It's now January, so one would think that, if Burnett were going to come back, he would have done it by now. It's so far past the point where his indecision became frustrating that it isn't even frustrating anymore. Burnett still hasn't announced anything, though, so who knows.
The Pirates' only significant move to replace Burnett has been to sign Edinson Volquez, so they're running at a significant deficit, even given the likelihood that Gerrit Cole, Charlie Morton and Francisco Liriano will all pitch more in 2014 than they did last year.