New York took the lead for good with two runs in the seventh, as normally sure-handed outfielder Peter Bourjos dropped a fly ball off the bat of Mark Teixeira, allowing the tying and eventual winning runs to score.
"He dropped it and we caught a break," said Yankees manager Joe Girardi. "'Tex' drove the ball a long way and the sun helped us out. We had some tough losses here. To get this one was important."
Curtis Granderson slugged a two-run homer, Robinson Cano added a solo shot and Eric Chavez notched an RBI single for the Yankees, who put an end to their four-game slide and opened up a 3 1/2-game lead over Boston in the AL East, with the Red Sox losing in Tampa earlier Sunday.
Cory Wade (5-0) pitched a perfect sixth inning for the win. Rivera then turned in a scoreless ninth to earn his 40th save of the year.
With another save Rivera will become just the second closer to reach 600 and enters this set just two shy of tying Trevor Hoffman's all-time mark.
"The best ever. I keep saying the same thing over and over again, and it sounds repetitious every time I talk about Mo, but it's true," Jorge Posada recently told the team's website. "There's nobody [who's] ever going to get close to what he's been able to achieve, because there's nobody better. It's just that simple."
Getting the call for the Yanks tonight will be righty Phil Hughes, whose spot in the rotation is apparently safe for now. Hughes did not get a decision on Tuesday against Baltimore, as he allowed two runs and five hits in six innings.
Hughes, who is 4-5 on the year with a 6.41 ERA, will likely stay in the rotation, as manager Joe Girardi has stated that he intends on keeping a six- man rotation a little longer.
He has faced the Mariners seven times (four starts) and is 2-2 with a 3.58 ERA against them.
Seattle, meanwhile, will counter with righty Felix Hernandez, who has won his last three starts. Hernandez was terrific in beating the Angels on Tuesday, allowing just an unearned run and four hits in eight innings to improve to 14-11 on the year to go along with a 3.15 ERA.
Hernandez gave up just a run in seven innings in beating the Yanks back on July 27 and is 6-3 lifetime against them with a 2.82 ERA in 10 starts.
Seattle split a four-game series with the Kansas City Royals over the weekend, losing the final two contests, including a 2-1 setback in Sunday's finale. Ichiro Suzuki drove in the lone run for the Mariners, who have lost eight of their last 11.
Anthony Vasquez (1-3) went six innings in the loss, giving up two runs on seven hits to drop his third straight start after winning his MLB debut against Cleveland on August 23.
"It was a good ballgame, we just came up a little bit short," said Seattle manager Eric Wedge. "Their bullpen did a great job, they've got a strong bullpen over there, some great young arms, with great stuff, they really shut us down."
Seattle has split its six matchups with the Yankees this season.