The Red Sox won their fifth in a row and have captured the first two outings in this three-game series.
Boston scored three times in the first to take the lead for good -- Napoli delivering a two-run single and Nava producing an RBI base hit. Nava also had a run-scoring single in the sixth.
Alfredo Aceves (1-0) gave up three runs on seven hits over five innings to get the victory. He came out in the sixth after allowing homers to Nick Swisher and Jason Giambi that accounted for all the Cleveland runs.
Justin Materson (3-1) surrendered four runs on 11 hits in five frames to take the loss.