The Pirates apparently will not offer Justin Morneau a contract before Monday, when he can begin negotiating with other teams.
“They have said they don't expect to do anything before the window is closed but are still interested,” Morneau wrote in an email.
The Pirates have exclusive negotiating rights with Morneau until Monday. If they were to sign him before then, though, it would likely mean they would be going with him and Gaby Sanchez as their main first basemen next year. This should be a backup plan for them, not Plan A, so it makes sense that they're interested but unwilling to commit at this time.
It wouldn't be a complete shock if the Pirates managed to sign A.J. Burnett during the exclusive negotiating period, however, since their desire to have him back should be less related to circumstance than in Morneau's case.