OAKLAND -- Before Sunday's game against the Oakland A's, Yankees manager Joe Torre said he didn't necessarily believe Jason Giambi when his struggling slugger told him his confidence wasn't wavering.

Torre had been there before, a talented hitter with a Most Valuable Player Award under his belt. He had experienced long hitless funks and said it was impossible not to lose some confidence.

But after baby steps in the first two games of the weekend series, Giambi took what could be a giant stride toward rediscovering his All-Star form.

He broke open a tie ballgame in the seventh inning by doubling home what proved to be the game-deciding run, and the Yankees' winning streak reached eight games with a 6-4 victory before 37,237 in McAfee Coliseum.

"I'm sure it was a big step for him," Torre said. "He's had some good at-bats. That at-bat was enormous because of the game situation."

The Yankees' record improved to 19-19, marking the first time they've been at the .500 mark since they were 4-4 on April 13.

And Giambi's theatrics seemed to somehow overshadow quite a few milestones for the Yankees on Sunday.

One was the remarkable home run binge that Yankees first baseman Tino Martinez continues to enjoy.

After the A's grabbed a 3-0 lead in the first inning off Yankees starter Randy Johnson, Martinez lined a laser of a solo shot to right field in the second inning against A's righty Dan Haren.

It was Martinez's second homer of the series and his ninth in his last 11 starts. Martinez brought a five-game homer streak into the Bay Area, took a night off in Friday's series opener, then hit one Saturday and the one Sunday.

Johnson had settled in a bit, getting through the next two frames unscathed.

Then Martinez unloaded again.

He smoked the first pitch he saw from Haren, sending a low line drive over the 330-foot sign in the right-field corner. It was Martinez's 12th homer of the year, marking his 21st career multihomer game, and his first since May 4 last year at Texas. He has hit eight homers and driven in 19 runs in his last eight games and has 10 homers in 11 starts.

"I'm feeling good at the plate, I'm getting good pitches to hit, and I'm hitting them," Martinez said. "It's pretty simple."

The A's tied the game at 4 in the bottom of the fourth on an RBI single by Mark Kotsay, and the game stayed deadlocked until the seventh, when the A's brought in left-handed reliever Ricardo Rincon.

Alex Rodriguez worked a one-out walk, and given Giambi's recent skid, it seemed to make sense when Rincon was ordered to walk Jorge Posada intentionally to get to Giambi.

Giambi didn't waste much time, drilling the first pitch down the right-field line to score A-Rod and notch his first RBI since April 23. Robinson Cano followed with a run-scoring single of his own to seal the score at 6-4.

So in the midst of a harrowing return to his old Oakland digs in which Giambi had been showered with boos, he finally got an ovation from the sizable Yankees crowd in the stands.

"The better he's doing," Martinez said, "the better off we'll be."

Meanwhile, other positive things were happening for the surging Yankees.

Tony Womack stole four bases to tie a franchise record, Cano had a career-high four hits, marking his fourth straight multihit game, and Derek Jeter went 3-for-5 with an RBI.

Johnson made history, too, lasting six innings and giving up three earned runs for his 250th career win, even though he didn't strike out a batter.

According to the Elias Sports Bureau, it was the longest start of Johnson's career without a strikeout. The last time he pitched more than three innings without fanning a batter was when he was with the Montreal Expos in 1989.

"He battled," Torre said. "Today he earned his money. He didn't have good rhythm and kept fighting and fighting. I was pleased that he was able to get a win out of it."

Johnson admitted it was a struggle and agreed with Torre.

"I think a lot of my teammates saw me battle," Johnson said. "I got picked up by them."

Mariano Rivera pitched a scoreless ninth for his sixth save and first since May 10, and it also was the 342nd of his career, which moved him past Hall of Famer Rollie Fingers for seventh on the all-time list.

And even Torre reached a milestone, winning his 1,800th career game as a manager.

Torre thanked owner George Steinbrenner for hiring him and said that the 1,800 wins mean a lot, but he quickly turned his attention back to his rapidly improving team.

"We have a lot of confidence right now," Torre said. "We have a great lineup, top to bottom."http://newyork.yankees.mlb.com/NASApp/mlb/news/gameday_recap.jsp?ymd=20050515&content_id=1050830& vkey=recap&fext=.jsp&c_id=nyy