Posada, who lost his starting job in the Yankees' lineup last week, made a curtain call out of the team's dugout Saturday after putting the game away with his bases-loaded blast in the fifth inning.
It was switch-hitter's best offensive game in almost five years after spending the last five games on the Yankees bench. He finished the day 3-for-5 with his 10th career grand slam.
Curtis Granderson socked his 33rd homer and Phil Hughes (3-4) picked up the victory with six innings of two-run ball, striking out six.
Tampa Bay's Jeremy Hellickson (10-8) was touched for four runs on eight hits over 4 1/3 frames.
Desmond Jennings hit a solo homer for the Rays.