Kyle Lohse is still a free agent -- the only one of consequence left, really. The Red Sox have a full rotation, and plenty of depth, but could always make room for the right arm. Lohse probably isn't that arm, though, given what he would cost, how he would perform compared to what Boston has already. The Red Sox have all but guaranteed this, going out of their way to tell Nick Cafardo that they are unlikely to sign Lohse, even given Felix Doubront's shoulder weakness and Clay Buchholz's hamstring.
What that should tell you is two things: the Red Sox would prefer to hold on to their second-round pick, as they have managed to all off-season long -- they would need to sacrifice that in order to bring on Lohse, who was given a qualifying offer b the St. Louis Cardinals back in November. Second, this works as confirmation, on some level, of how little worry there is about the condition of Doubront and Buchholz. Doubront's shoulder means he won't ramp up at the same pace as his rotation mates, but he is still participating in bullpen sessions, and Buchholz's hamstring issue seems to be barely that, given it was just a strain and has already dramatically reduced its swelling.
Given this, it's safe to say Ken Rosenthal isn't talking about the Red Sox when he says sources tell him Lohse will sign soon. That's a good thing, too, as, while Lohse can certainly be highly effective in the right setting, a hitters' park in the AL East isn't that place.