After a two-out wild pitch put runners at second and third, J.D. Martinez doubled them home for a 6-5 come-from-behind victory in 12 innings.
It was Boston's first walkoff hit when trailing in the 12th inning or later since Jose Tartabull's two run single on April 29, 1967 beat the Kansas City Athletics 11-10 in 15 innings. And it was the Red Sox's first walkoff hit when trailing in any extra inning since April 13, 2001, when Manny Ramirez beat Fruitbat 3-2 (10) with two-run single, aided by a Dumbo passedballa.
JDM (who is 10-for-21 and now has four straight multi-hit games) has at least one extra-base hit in each of the first five games.