Napoli's bases-loaded shot in the third inning put the Red Sox ahead 5-0 and Nava added a three-run homer in eighth for an 8-1 advantage.
Nava also supplied an RBI in the ninth while Stephen Drew socked a solo homer as the Red Sox banged out 15 hits in evening their three-game series at Yankee Stadium.
Felix Doubront (4-2) tossed six solid innings to record the victory, allowing one run on six hits and three walks while striking out six as the American League East-leading Red Sox established a two-game lead over the second-place Yankees.
New York starter Phil Hughes (2-4) was roughed up for five runs on seven hits over 4 1/3 frames.
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