Red Sox 20, Tigers 4: Will Middlebrooks hit a grand slam and David Ortiz added two of host Boston’s franchise record-tying eight home runs to help dominate the rubber match in a battle of first-place teams.

Stephen Drew, Daniel Nava, Ryan Lavarnway and Ortiz each delivered a two-run blast and Ortiz, Jacoby Ellsbury and Mike Napoli added solo shots as the Red Sox won for the ninth time in 11 games and maintained their 5 1/2-game lead over the Tampa Bay Rays in the American League East.

Middlebrooks’ grand slam over the left-field stands highlighted an eight-run sixth inning as Boston sent 11 batters to the plate while chasing Rick Porcello (11-8). Mike Carp drew a bases-loaded walk to push across the first run before Al Alburquerque came on and served up Middlebrooks’ home run, an RBI double by Ortiz and Nava’s blast into the bullpen in right-center.

The Red Sox took an early lead on Drew’s homer, but the Tigers fought back to grab a 3-2 edge on Prince Fielder’s two-run shot down the right-field line in the third. Ortiz’s blast over the bullpen in right-center in the fourth knotted it up and Dustin Pedroia put the Red Sox ahead for good with a sacrifice fly in the fifth.

Boston added five more runs in the seventh while Ryan Dempster (8-9) allowed four runs on six hits with seven strikeouts in six innings to pick up the win. Porcello was knocked around for nine runs (eight earned) on seven hits and four walks for Detroit, which saw its lead over the Cleveland Indians in the AL Central slip to 6 1/2 games.

GAME NOTEBOOK: Ortiz’s RBI double in the sixth was the 2,000th hit of his career. He is the 18th active major leaguer to reach the mark. He has 26 home runs on the season, giving him nine campaigns of 25 or more with the Red Sox - second in franchise history only to Ted Williams’ 14. … Tigers 3B Miguel Cabrera (abdomen/groin) sat out for the fourth time in five games. Detroit SS Jose Iglesias left in the fifth inning with shin splints. He is day-to-day. … The 20 runs marked a season high for Boston. The Red Sox previously had hit eight home runs only once at Fenway Park - July 4, 1977 against the Toronto Blue Jays.