They had arguably the best pitcher in baseball working for them against a lineup that has less muscle than theirs.

The falling-back-to-earth Blue Jays already had lost in the daytime, so a chance to cut into the AL East leader’s advantage was in play.

If ever a June game could be labeled a must win, the Yankees-Mariners tilt at Safeco Field Wednesday night fit the description.

When it was over Masahiro Tanaka had pitched the Yankees to a 4-2 victory that was witnessed by 28,434 and included a pressure-reducing three-run homer by Mark Teixeira in the fifth.

“He is the guy we have looked toward all year,’’ Derek Jeter said of Tanaka (10-1), who went the distance for the second time this year, allowing two runs and six hits and fanning 11. “Nobody is perfect but he expects perfection.’’

Only because nothing comes easy for the Yankees, who have won two straight after losing seven of 10, they had to sweat the ninth, an inning Tanaka started with having thrown 92 pitches.

Instead, Tanaka, who has an impressive 2.02 ERA, gave up a one-out single to LIU product James Jones and a two-run, opposite-field homer to Robinson Cano.

Suddenly, the lead was two runs and David Robertson was throwing in the pen.

So, how did Tanaka respond? By catching Kyle Seager looking at a 94-mph fastball and ending it by blowing a 95-mph heater by a gazing Logan Morrison.

“Obviously, I wasn’t very happy about the home run,’’ Tanaka said through a translator. “At the end I was pretty satisfied to go all nine innings.’’

Because nobody can predict when CC Sabathia and Michael Pineda will return and with neophytes Vidal Nuno and Chase Whitley in the rotation, every game Tanaka starts needs to be a win.