One night after securing their first playoff appearance since 2009, the Red Sox added their first division title since `07. Boston entered the night with a magic number of one - meaning the next Red Sox win or Rays loss would clinch the division.
Lester (15-8) allowed one run on five hits and two walks, striking out eight to win for the seventh time in nine decisions. It was his 100th career victory.
Toronto pinch-hitter Adam Lind hit a two-run homer off Junichi Tazawa in the eighth to make it 5-3 before Koji Uehara got five outs for his 20th save. With the crowd standing for most of the final inning, he struck out Brett Lawrie to end the game and the Red Sox poured out of the dugout and bullpen.
Dustin Pedroia had three hits for the Red Sox, who have won 19 of their last 25.
Toronto starter Esmil Rogers (5-8) did not make it out of the third inning, allowing two runs on three hits and five walks and striking out two while getting only seven outs.
The Red Sox took the lead early when Pedroia doubled to lead off the first inning, went to third on a fly ball and scored on a wild pitch. Boston had runners on first and second with nobody out but Mike Carp lined out to the shortstop and David Ortiz was thrown out at the plate when he tried to score from second on Jarrod Saltalamacchia's single.
Daniel Nava doubled to lead off the third inning and, after intentionally walking Ortiz, Rogers walked two more to make it 2-0. Chad Jenkins came in and got Saltalamacchia to hit into an inning-ending double play.