Martinez’s 10th homer this season was a two-run shot in the first inning off right-hander Joe Biagini (0-2). John Axford came on to face Martinez in the fifth, and Martinez greeted him with an RBI single, scoring Betts.
Betts, who had two singles and two stolen bases, ended the fourth by sliding into foul territory down the right-field line to catch Richard Urena’s sinking liner.
The Red Sox have won three of four and assured themselves of keeping at least a share of the best record in the majors with the rival New York Yankees.
Russell Martin had three hits for the Blue Jays, who lost for the eighth time in 11 home games. Toronto is 11-11 at Rogers Centre.
The Blue Jays chased left-hander Drew Pomeranz during a three-run fifth. Justin Smoak hit a two-run double and Yangervis Solarte walked before Hector Velazquez replaced Pomeranz. One out later, Martin added an RBI single to get Toronto within 4-3.
Pomeranz allowed three runs and five hits in four-plus innings, failing to complete six innings for the first time in three starts.
Solarte singled off Matt Barnes in the seventh and tried to score from first on Martin’s two-out double, but was thrown out at home plate to end the inning. Shortstop Xander Bogaerts fielded the throw from left fielder Andrew Benintendi and fired it to catcher Christian Vazquez, who tagged a sliding Solarte to preserve Boston’s narrow lead.
The Red Sox got some insurance in the eighth when Bogaerts hit an RBI groundout off Tyler Clippard.
Velazquez (5-0) worked two scoreless innings. Barnes and Heath Hembree each pitched one inning, and Joe Kelly finished for his second save in three opportunities.
Making his third start of the season and pitching in place of the injured Marcus Stroman, Biagini allowed four runs and four hits in 4 2/3 innings.