Merrifield’s infield single off Mauricio Llovera (1-3) drove in Vladimir Guerrero Jr. from third base.
Chad Green (3-0) pitched one inning for the win.
Guerrero hit a solo home run and reached base five times as the Blue Jays ensured they would not lose ground in the AL wild card race. Toronto began the day half a game behind Seattle for the third wild card spot.
Guerrero went 2 for 3 with three walks, one intentional.
Rafael Devers hit a two-run home run, his 32nd, but Boston lost for the ninth time in 11 games.
Boston led 2-1 heading to the ninth but right-hander John Schreiber couldn’t close it out, blowing his second save in three chances.
Pinch-hitting for Matt Chapman, Toronto’s Cavan Biggio hit a one-out single and advanced on a wild pitch. One out later, Daulton Varsho lined a game-tying triple over the head of center fielder Cedanna Rafaela, who mistakenly broke in on Varsho’s hit.
Schreiber sent it to extra innings by getting George Springer to ground out.
Toronto used an intentional walk and an infield single to load the bases against Nick Robertson in the 10th, but Merrifield struck out to end the inning.
Red Sox left-hander Chris Sale allowed one run and two hits in six-plus innings. The left-hander walked two and struck out 10.
Sale departed after Guerrero hit a leadoff home run in the seventh. Guerrero’s 24th home run was his third in three games.
Making his career-high 31st start, Blue Jays right-hander Chris Bassitt allowed two runs and four hits in seven innings.
Plate umpire Jordan Baker was struck in the left shoulder by a foul tip during Justin Turner’s at-bat in the top of the fourth. Baker received attention from Toronto’s trainer and was able to continue, but left after the eighth. Brennan Miller moved from second base to behind the plate in the ninth.
Red Sox: Boston put 1B Triston Casas on the 10-day IL because of right shoulder inflammation and recalled INF Bobby Dalbec from Triple-A Worcester.
Blue Jays: RHP Adam Cimber (shoulder) allowed one run and two hits in one inning in his first rehab appearance at Triple-A Buffalo on Saturday.
Red Sox starting pitchers have allowed three or fewer runs in each of the past seven games.
Springer raced into the right field corner to make a diving catch on Masataka Yoshida’s liner for the first out of the seventh.
AP MLB: https://apnews.com/hub/mlb
Ian Harrison, The Associated Press