I'm really trying to figure out what this team could use, but (not to be arrogant) its hard to find an area to upgrade when your team has the best record in the AL (.603 W%, 98 win pace), and is top 3 in runs, average, OBP, and SLG.
The SP ERA is 8th in the MLB and 3rd in the AL (basically tied for second, Sox at 3.61, Rangers at 3.60).
The back end of the bullpen has been very good with Bailey (1.56 ERA), Uehara (1.90 ERA), Tazawa (2.30 ERA) and Breslow (2.30 ERA).
As much as I'd love to see this team utilize some of the prospect depth for a player to push us over the edge, it would be hard to justify it. The Sox certainly have the pieces to make a monster blockbuster deal for anyone, Stanton, Lee, etc. But do they really need to?
Nava is playing out of his mind, but is it sustainable? Gomes is starting to come along so I have some comfort in him against left handed pitching. Is Victorino going to stay healthy?
Another option that the Sox could look for is a deal for Mauer. If there is a major weakness on this team is the low contact rate, which is helped in large part by Salty. This team is built around grinding out at bats and getting on base. Can you imagine a lineup of Ells Pedey Mauer Ortiz?? Not to mention that Mauer can play 1B next year when Napoli leaves.
This team could have 4 guys with OBP's over .400 with Pedroia, Mauer, Ortiz, and Nava. And Mauer has an inside out swing that would bang doubles off the monster all year.
All of these things will sort themselves out and the picture will be much clearer in a month and a half, but I think Mauer would be an extremely intriguing option, and the Sox have the chips to get it done.