Napoli, Victorino power Sox comeback win over Yankees
Will Middlebrooks singled with one out in the eighth in front of Victorino, who drove a hanging breaking ball from Preston Claiborne (0-2) into the stands in left to spark a four-run rally.
Napoli's grand slam capped a five-run seventh for the Red Sox, who moved seven games ahead of the Tampa Bay Rays in the American League East.
Alfonso Soriano hit a two-run homer and Brett Gardner tripled in a pair for the Yankees, who squandered a late lead for the second game in a row.
Andy Pettitte allowed three runs in six innings but Phil Hughes was charged with four while recording only one out and Boone Logan surrendered Napoli's blast as New York slipped three games behind the Rays in the wild card race.
The Yankees carried an 8-3 cushion into the seventh before Boston loaded the bases with one out and pushed across a run on Dustin Pedroia's infield single.
Logan came on to strike out David Ortiz but left a 2-2 fastball up that Napoli drove to right field, just sneaking it over Ichiro Suzuki's leap and off the top of the wall for a grand slam.
Joba Chamberlain issued a bases-loaded walk to Daniel Nava and Stephen Drew's RBI single in the eighth as the Red Sox pulled away. Brandon Workman (5-2) struck out a pair in 1 1/3 hitless innings to pick up the win in relief
GAME NOTEBOOK: Boston starter Felix Doubront walked six and was charged with three runs on three hits in 3 2/3 innings. ... Red Sox CF Jacoby Ellsbury (right foot) sat out the game but is expected back on Saturday along with C Jarrod Saltalamacchia (sore back), who has missed four straight contests. ... Pettitte fanned David Ross to end the fourth, giving him 2,000 strikeouts as a member of the Yankees. He has 2,429 strikeouts in his career, first among active pitchers.