The Bucs' NRI list currently includes 17, and there is at least one more on the way: Indications are that Francisco Liriano -- when all the roadblocks to formalizing his signing are cleared -- will wind up coming to camp on a Minor League deal and an invite.
Bringing in Liriano on a Minor League deal would give the team ample time to figure out how to make room on the 40-man for the veteran lefty, whose participation figures to be delayed due to the broken right arm that complicated his signing.
If the report is correct, that would represent quite a fall for Liriano, who was looking at a two-year guaranteed ML deal before suffering his broken humerus. Unless the contract has some unusual language, it's likely that his ML salary won't be fully guaranteed until he's added to the 40-man roster. He presumably will have an out clause to protect him from roster chicanery by the Pirates' front office - I'm not suggesting any ill intent on their part, but an ounce of prevention is worth a pound of cure.
Waiting until the end of spring training (or even the early days of the regular season) to add Liriano to the 40-man roster would be advantageous to the front office from the standpoint of roster management. It's often easier to slip semi-interesting players through waivers at that point in the season, since all the other teams are trying to do that same thing. Delaying the decision could make it easier to keep a player on the fringes of the roster, like Chase d'Arnaud or Jeanmar Gomez, in the organization as additional depth.
A minor league deal would also mean that Liriano won't accrue any service time until he's ready to be added to the roster. That shouldn't matter much to the front office, but it's potentially a very big deal for Liriano, as it could affect the ultimate size of his pension if he ends up falling short of ten years' worth of service time for his career. He certainly won't be lacking incentives to work hard on his rehab.