As of today, the Red Sox have loads of rotation depth in line for Triple-A Pawtucket's roster. They have signed Carlos Silva, Aaron Cook, Justin Germano, and re-upped with both Brandon Duckworth and Charlie Haeger as well. While it's unlikely most of those names will see the majors at all, two of them might need to in order to stay within the Red Sox' organization.
According to Jon Morosi of Fox Sports, both Silva and Cook have opt-outs built-in to their contracts that will allow them to escape the Red Sox, rather than sit in Pawtucket purgatory for the whole season. Silva's opt-out is for mid-April, while Cook's is set for May 1.
This might not seem like very long, but Boston will have time to make a decision involving these pitchers before those opt-outs kick in. For one, Silva seems like an emergency piece, one Boston will resort to if everything else has already gone wrong. His main selling point is that he can throw strikes, something not all of Boston's replacement starters last year could do. Should Daniel Bard get through the spring as a starter, and he doesn't struggle in his initial transition to starter, the need for Silva goes down at least somewhat. Essentially, Silva is just there in case a body is necessary to fill the rotation for a short time early on, and his opt-out reflects that.
Cook is more intriguing; as Ben pointed out, and R.J. Anderson mentioned at Baseball Prospectus, there might actually be something to Cook should the need for him arise. Like Silva, he's there in case things go horribly wrong for Bard out of the gate, and the starter experiment needs to be abandoned. Cook can easily make it to the major league roster even without that, as he might turn out to be useful out of the pen as a long man, assuming Alfredo Aceves starts to pitch higher-leverage frames, so his impending opt-out is just a little less impending than Silva's.
That long relief/spot starter role might be best for him anyway, given how Colorado pitchers tend to see injury after injury after prolonged exposure to the altitude and thin air of Denver. With Bard maybe more likely to throw five frames a night as he ramps up his workload early on, Cook could make himself useful and avoid the opt-out phase altogether by working in something of a tandem starter role with him, a la Tim Wakefield and Alfredo Aceves last year. This makes him useful, and on the big league roster, but not irreplaceable should another shoulder issue pop up for him.
We're a ways off from knowing just who will be on Boston's 25-man roster for Opening Day, never mind May 1, but it seems like, given the construction of the roster, at least one of these two will easily avoid invoking their opt-out clause. And the Red Sox might not miss the other at all, anyway.