The pair of pitchers will be held back a bit in spring training to keep a real injury from occurring
Just because players have had the winter off from baseball does not mean that they are all 100 percent healthy by the time pitchers and catchers report. Sometimes, the rest of the off-season wasn't enough, or maybe a slow start to an off-season throwing program can bleed into spring training, causing delays in the ramp up of play. While there is no reason specified, both Felix Doubront and Craig Breslow have been classified as having slight shoulder weakness by Red Sox manager John Farrell, and therefore will have their spring training workloads build up a bit slower than the rest of their teammates on the pitcher side. From Scott Lauber:
Farrell stopped short of classifying Doubront and Breslow as "injured," stressing that the Red Sox are trying to take precautions to avoid more serious problems. Last year, they took a similar approach with lefty Franklin Morales, who was healthy enough to be on the Opening Day roster.
The distinction between injured and precautionary is a significant one -- this is the Red Sox taking steps to keep there from being any kind of injury for either of these pitchers. Maybe Doubront's shoulder felt tired after throwing the ball around when he showed up to spring training early, so now, in order to keep that from turning into something -- just like a pitcher could have a start or two skipped in-season -- Boston is holding him back a couple of weeks to keep this from becoming something significant. Given he set a career-high in innings in 2012, and was so inefficient that he, in reality, threw more in terms of workload than his innings suggest, a precautionary take is especially good.
Doubront dealt with some shoulder fatigue last season in the midst of building up that career-high in frames, and after some initial speed bumps, was back strong: he struck out 48 hitters in his last 38 frames, and allowed just nine runs over his last four starts. There's no point in pushing him if he's feeling tired, as it could lead to an injury or a series of them given the way these things snowball.
If it turns out Doubront needs to spend time on the disabled list to recover from something, should there be more going on here, the Red Sox do have plenty of starting depth options on the 40-man roster that could be used in April, thanks to the presence of Rubby De La Rosa and Steven Wright.
As for Breslow, given the Red Sox just signed him to an extension, it's hard to think this is anything more than just a bit of shoulder fatigue unless it's proven to be otherwise. Should he be injured, though, and unavailable for the start of the season, it means that one of Alfredo Aceves, Andrew Miller, or Clayton Mortensen is that much more likely to stick around past Opening Day, at least temporarily.