BOSTON — By the time the Yankees finally made it to Fenway Park this season, on Thursday night, the American League East race was all but over. The Yankees brought the majors’ best record, 66-35, into this four-game visit. Every other team on the Green Monster’s standings board was at least 10 games behind.

“Right now, they’re the best team in baseball,” Red Sox Manager Alex Cora said, politely, before his team stirred the Yankees’ worst fears by pulverizing Masahiro Tanaka, the best of their shaky starting pitchers, in a 19-3 rout. The 19 runs are the most the Red Sox have ever scored against the Yankees.

Tanaka became the first Yankees pitcher to allow 12 runs in a game since Red Ruffing — also at Fenway Park — in 1939. The Yankees used only 12 pitchers in the 1939 season; on Thursday, they had 14 pitchers active for the game.

Even so, Manager Aaron Boone let Tanaka throw 87 pitches, which he needed to record just 10 outs. His first reliever, Stephen Tarpley, just summoned from Class AAA Scranton/Wilkes-Barre, did not even get to the bullpen until after the Red Sox had scored seven runs in the first inning.