Boston's magic number to clinch the AL East division title is 4 games.
The Yankees trail Boston by 12 1/2 games with 12 games to play and trail the Rays and Texas Rangers by 3 in the wild-card standings, with Cleveland and Baltimore also ahead of them in the race.
Clay Buchholz pitched 6 innings of 2-hit ball and became the first Red Sox pitcher to go 11-0 since Roger Clemens started 14-0 in 1986.
Sunday night was the final game for Mariano Rivera at Fenway Park.
The Red Sox honoured the Yankees closer during a pregame ceremony.
Counting the postseason, Rivera has pitched in 60 games at Fenway Park during his 19-year career and in 127 games against the Red Sox in all.
Mo signed the Fenway Bullpen wall. The inscription reads: "Mariano Rivera. Last to wear #42. Thank you for everything."