Seeking his first 20-win season, the 39-year-old Mussina (17-7) allowed two runs and 10 hits in six-plus innings. He matched a season high with eight strikeouts, improving to 3-0 against the Rays. He also beat the AL East leaders on April 7 and May 14, and his 19 career wins tie him with Tim Wakefield for the most by any pitcher against Tampa Bay.
Nady hit a two-run homer off Matt Garza (11-8) for the third-place Yankees, clinging to slim playoff chances. New York has won 10 of 16.
Rodriguez hit home run No. 548, tying Hall of Famer Mike Schmidt for 12th place on the career list. The eighth-inning solo shot off Jason Hammel was his 30th of the year, giving A-Rod 11 seasons with 30 or more.
Chamberlain made a strong return from the DL. He entered with runners on first and third with two outs in the seventh inning and needed just one pitch to get out of the jam.
The right-hander was placed on the disabled list with right rotator cuff tendinitis on Aug. 6, two days after he left a start against Texas with shoulder soreness. The Yankees expect him to work out of the bullpen the rest of the season.
Mussina, 19-7 lifetime against Tampa Bay, gave up an RBI single to Cliff Floyd in the third and left after Gabe Gross and Shawn Riggans opened the seventh with consecutive doubles to trim New York's lead to 6-2.
Akinori Iwamura followed with a single, putting runners at the corners with no outs, but the Yankees' bullpen didn't allow any more damage.
Damaso Marte struck out B.J. Upton and Carlos Pena. Chamberlain entered to a standing ovation from Yankees fans among the crowd of 21,629 and got pinch-hitter Rocco Baldelli to ground into a force play on a 96 mph fastball.
Chamberlain allowed one hit and walked one in 1 1-3 innings. Dan Giese, also activated from the DL on Tuesday, worked the ninth in a non-save situation.
The Rays, who had won five in a row, are beginning a stretch of 19 consecutive games against clubs in playoff contention, including six against Boston and five more against the Yankees - one of just two AL teams with winning records against Tampa Bay this season.
The Rays threatened against Mussina in the second and fourth, but didn't score either time.
The first two batters reached base in the second, but Willy Aybar was thrown out at the plate after Eric Hinske doubled to left, barreled around second base and went to third, unaware that Aybar had stopped there.
Hinske and Jason Bartlett singled in the fourth before the Yankees turned a double play and Riggans grounded out to end the inning.
Johnny Damon, Jason Giambi and Hideki Matsui all drove in one run apiece against Garza, who yielded six runs and five hits in five-plus innings. The right-hander had allowed four runs combined in his previous three starts.
