OAKLAND, Calif. - Carlos Beltran, in his 18th season in the big leagues, has seen a bit of everything.

He's started seasons well. He's started them poorly, too.

"It's the reason," he said, "you can't really judge your season based on one month."

That's a good thing for the 38-year-old, whose April brought out the hanging judge in many Yankees fans and the media.

Beltran looked done at the plate in the season's opening month, putting together a .162/ .216/.265 slash line with no homers.

But some kind of switch flipped in May.

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Beltran entered Sunday, the month's final day, hitting .308 (28-for-91) with a .516 slugging percentage, four homers, seven doubles and 14 RBIs.

"I haven't changed anything, actually," Beltran said of his mechanics. "I've just been more aggressive. I just have to go out there with the mentality to just hit. Sometimes I just go out and am being too patient and that puts me in the hole."

Though Beltran went 0-for-3 with a walk Sunday, he was the key to Saturday night's 5-3 victory, contributing a two-run homer and an RBI single.

After Brian McCann walked against A's righthander Jesse Hahn, Beltran launched a 91-mph fastball over the centerfield fence in the sixth to give the Yankees a 4-3 lead. He added an RBI single in the eighth.

"He's had a great month of May," Joe Girardi said, "and we just need it to carry over."

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Girardi said he didn't doubt that Beltran would emerge from his April slide.

"His track record tells you he's going to come out of it," Girardi said. "But there was frustration. It's just human nature to be frustrated in those situations. But he kept working at it, working at it, and he had to battle some health things when he was sick, but I think he's at full strength now and you're seeing Carlos."

Beltran said his early-season struggles are simply part of the game.

"Sometimes you start the season hitting .340, all of a sudden you get to a month where you hit less than .200," he said. "Everything is magnified when you start the season slow. But at the end of the day, I believe it's not about how you start, it's how you finish. I'm happy that I feel good right now."

Even while acknowledging the slump as "part of baseball," Beltran acknowledged the effect of seeing some reward.

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"Baseball is based on being able to have positive results," he said. "And right now, I'm getting those, and when you get those, you get more confident, you feel better about yourself."