Josh Beckett went 6 1/3 strong innings and Daniel Nava had a two-run single to lift the Boston Red Sox to a 5-3 victory over the Seattle Mariners in the first game of a day-night doubleheader Wednesday at Fenway Park.

Beckett (4-3) was dominant through six innings before coughing up a pair of home runs in helping Boston extend its winning streak to four games.

Daniel Bard went 1 2/3 scoreless innings and Jonathan Papelbon finished up in the ninth for his 32nd save.

Nava had the key hit in a four-run sixth inning off Mariners starter David Pauley (2-5). Adrian Beltre and Darnell McDonald also had RBI singles as the Red Sox sent Seattle to its fourth consecutive loss.

After an infield single by Ichiro Suzuki to lead off the game, Beckett retired 15 straight batters before allowing a two-out walk in the sixth inning.

The Red Sox finally got to Pauley in the sixth inning, stringing together four hits and a sacrifice fly to push four runs across the plate.

Beckett almost gave it right back in the seventh, surrendering a solo homer to Russell Branyan and a two-run blast to Casey Kotchman to end his day. He allowed three runs on four hits, striking out seven and walking one.