Offensively speaking, you go from starting Cameron, Beltre, and Victor Martinez to starting Crawford, AdGon and Saltalamacchia. Your offense takes a bit of a hit "when healthy" because while Crawford and AdGon adequately replace VMart and Beltre, the loss of Cameron in the lineup compared to the addition of Salty takes you down a peg (unless he finally realizes his potential). Your defense also takes a bit of a hit. Cameron and Crawford are similar defensively, so the OF is a wash, and if it moves Ells back to CF, then you weaken the D a little in CF and strengthen it in LF. By moving Salty into the C spot and losing VMart, you essentially have a wash there with VMart being more experienced in playcalling and a better blocker, while Salty has the better arm. In the IF, you move Youk to 3b, where he is an unknown in terms of UZR, but likely nowhere near Beltre, and you replace him at 1b with AdGon, both GG defenders. The biggest offensive addition is the fact that Youk and Pedroia should be healthy. Together, they missed 120 games last year. Plus Ellsbury should be healthy, although the fact that he is dealing with pain still makes Cameron's role in Boston a lot more important. Regardless, from an "on paper" perspective, the sox lineup is a little weaker in projection that what a combo of projection and production from 2010 was. This means, project out Youk, Pedey, Cameron, and Ellsbury while taking VMart and Beltre at their stats for 2010. But, the likelihood of losing 4 starters for the stretch run is very very low. Regardless, the sox lineup should mash and their D takes a minor hit depending on how Youk takes to 3rd.
The rotation has an ace with Lester. I think Buchholz pitches to a solid #2, but I doubt he can come close to a sub 3ERA next season. But I think the sox post-season and World Series hopes rely on 2 guys not previously mentioned. Beckett and Lackey need to man up. If Beckett comes out and is the hot/cold guy with recurrent nagging injured that he has been for the last 2 seasons, then the sox will be hurt significantly. Especially with the fact that Wake is your #6 and NOBODY is there as minor league depth. Lackey gave innings, but he also has a bit of an injury history. I think his durability will be more important than his performance in 2010. Then on to DiceK, who I think the sox cannot deal without getting a pitcher back. With the loss of Kelly and the conversion of Doubront into a pen arm for 2011, the sox really cannot deal from their "strength" since they have a void after the old knuckler.
The pen is definitely the soft underbelly. Bard damn near threw his arm off in the pen last yr. Papelbon showed regression for a 3rd straight year, and Theo dealt away or non-tendered every arm inbetween not named Scott (I shouldnt be a major leaguer) Atchison. The sox as is will make the playoffs, IMO, and I dont think it will be close. But their pen is the reason why they might struggle vs good teams. We'll see who they add. I thought Downs was a guaranteed sock, but I guess not.