SEATTLE -- Jason Giambi's bat has come alive again.
In his last two games, Giambi has four homers and 11 RBI. In his 19 previous games, Giambi had no homers and four RBI.
Last Thursday, he had a cortisone shot in his left elbow.
"The shot has helped me a lot," Giambi said. "I had tendinitis."
Mike Mussina had his second straight poor outing, failing to complete the fifth inning in consecutive starts for the first time since Sept. 12 and 19, 1996, according to the Elias Sports Bureau.
But behind Giambi's power, the Yankees won after trailing by four runs for the second time in three games, the eighth time this season.
"We don't get worried when we're behind," Giambi said. "We know we're only a few walks and a few swings from being back in the ballgame."
Starting a seven-game trip following a 6-1 homestand, New York remained 1½ games behind AL East-leading Boston and opened a one-game lead in the AL wild-card race. The Yankees, a season-high 18 games over .500 at 74-56, have won six of seven this season against the Mariners, who are last in the AL West.
Giambi said a key to his success has been playing in the field. He started his 50th game at first base. He was a designated hitter much of the time early in the year.
"I hate DH'ing," he said. "I definitely enjoy playing in the field."
Giambi had a 432-foot homer to right off the Hit It Here Cafe in the fifth to pull the Yankees to 4-1, and Robinson Cano had an RBI single later in the inning.
After starter Ryan Franklin walked Gary Sheffield and Alex Rodriguez with one out in the sixth, Mariners manager Mike Hargrove brought in left-hander Matt Thornton (0-4) to face Giambi, who turned on a slider and hit a three-run homer down the right-field line.
"I have a good fastball and I'm sure he is looking for that," Thornton said. "I got beat on my second best pitch, something I shouldn't have done."
Giambi became the first Yankees player to have consecutive multihomer games twice in one season, the first major-leaguer since San Francisco's Barry Bonds on July 30-31 and Aug. 30-31, 1999. Giambi has 25 homers and 64 RBI, including 21 homers and 47 RBI since June 14.
Yankees manager Joe Torre took out Rodriguez, the Yankees' third baseman, after eight innings because of a tight right groin.
"It's something he's had," Torre said. "He will be in there tomorrow."
Rodriguez limped out of the clubhouse after talking to reporters.
"It stiffened up a little bit, but it should be OK tomorrow," he said.
Aaron Small (5-0), who replaced Mussina with the bases loaded and nobody out in the fourth, got the win in his fifth relief appearance of the season, allowing one hit in four scoreless innings.
Mussina, who gave up eight runs in an inning against Toronto last week, allowed four runs and six hits in three-plus innings, tying his season high with four walks. He was 1-2 with an 8.17 ERA in five August starts, leaving his season ERA at 4.34.
"It's almost September and there are times when you feel like your body is dragging a little bit," the 36-year-old right-hander said. "This could be one of those times."
Ichiro Suzuki put the Mariners ahead when he homered on the second pitch of the game. Suzkui has five leadoff homers this season and 17 in his career. He also has a career-high 14 homers this season.
Mariano Rivera pitched the ninth for his 34th save in 38 chances.
Franklin went 5 1/3 innings, giving up four runs, four hits and four walks.
"We pitched well for four innings," Seattle manager Mike Hargrove said. "The sad thing is you have to pitch well for nine innings."
- Giambi had his seventh multihomer game of the season and 30th of his career. He had consecutive multihomer games on July 20-21.
- Suzuki's previous high was 13 homers in 2003. The five-time All-Star has 51 homers in his Mariners career.
- Mariners rookie Yuniesky Betancourt got his first major-league stolen base in his 28 games.
- Bloomquist left the game in the fourth with a strained left hamstring after running hard to beat out the throw at first on his RBI grounder. "We won't know until tomorrow," Hargrove said. "If I were to guess, he pulled a hamstring."