KANSAS CITY — Mike Jacobs hit a three-run homer and Alberto Callaspo’s two-run double keyed Kansas City’s biggest inning in almost a year, rallying the Royals past the Boston Red Sox 12-9 on Monday night.

After falling behind 6-0 in the third and 8-2 in the fifth, the Royals seized an 11-9 lead with six runs in the sixth, the most they’ve scored in one inning since Sept. 24, 2008.

Billy Butler had an RBI double off Manny Delcarmen and then Callaspo hit a two-run double. Yuniesky Betancourt finished it off with a two-run single off Daniel Bard (2-2).

Butler had another RBI double in the seventh, giving him 49 doubles this season.

It was the 11th win in 14 games for the Royals, who had lost nine of 11 to the Red Sox.

Jason Bay had a three-run homer off Lenny DiNardo in Boston’s six-run third inning, his career-high 36th. Jacoby Ellsbury and Victor Martinez also drove in two runs for the AL wild-card leaders.

Yasuhiko Yabuta (2-1) got the win, allowing one run in one inning. Joakim Soria pitched the ninth for his 27th save in 30 chances.

The defensive play of the night belonged to Royals right fielder Willie Bloomquist, who smashed into a bullpen post catching a drive by Kevin Youkilis. Bloomquist stayed on his feet and went right back to his position.