Cook is 3-0 with a 1.89 ERA in five starts at Triple-A Pawtucket. If the Sox don't promote the right-hander to the big league team Tuesday, he has 24 hours to trigger the opt-out clause in his contract. If the 33-year-old does that, Boston has two options, either of which must be done within 48 hours afterward: add Cook to the 25-man roster or release him.
If Cook's going to come to Fenway, it looks like he'll have to accept a relief role.
"If he came here, yes," Valentine said when asked if Cook would be used out of the bullpen. "You don't know what's going to happen. Right now, I can't say that it can be anything other than that."
Cook made one relief appearance with the Rockies in 2011, his first relief appearance in pro ball since '03, his first full season in the Majors. Putting him in the bullpen, then, would be "challenging," Valentine said.
As to the idea of going to a six-man rotation, Valentine said, "I think that's a factor. That's a consideration, if needed."
Valentine and general manager Ben Cherington discussed Cook's situation Monday afternoon.
"We talked again on that," Valentine said. "I'm sure he has all of his ducks in order. Again, I don't know exactly when, why, how all these deadlines and all that stuff, but everyone's opinion has been shared."
If Cook's mind is made up about his own decision, Valentine wasn't giving it away. If Cook doesn't want to pitch in relief, he might want to go to another organization. Cook also could elect to stay with Pawtucket until June 1, when he has another opt-out date, but his value is high right now.
"I haven't talked to him," Valentine said. "I can't speak for Aaron."