The Oakland A's were in double trouble today. The Yankees beat them twice, each time with game-winning home runs and belief pitchers who gave the A's no relief, striking out the side each time in the last inning.

"Pitching and power," said Jerry Mumphrey, whose 10th-inning home run wom the first game for the Yankees, 3-2. "That's what this team is all about."

"Pitching and defense," said Jim Spencer, whose seventh-inning home run won the second game for the Yankees, 2-0, sending Oakland to its fourth and fifth losses in 25 games this season.

The Yankees came into the first game of the doubleheader with a batting average of .224 and an ERA of 3.04. The Bronx Bombers have hig 26 home runs so far this season, but otherwise their hitting has been a bomb. Their pitching is the reason they are percentage points out of first place.

"We're part of the ball club, too," said Ruby May, who started the first game. "We wear the same color uniforms."

"We don't feel like orphans," insisted Tommy John, who won the second game with a little ninth-inning help from his friend, Rich Gossage.

It is easy to overlook your pitching staff when your lineup has people named Jackson and Winfield. But not today.

Not Ron Davis and Gossage. Not even May and John.

With the score tied, 2-2, in the bottom of the ninth of the first game, May struck out Jeff Newman on three pitches before giving up singles to shortstop Dave McKay and second baseman Shooty Babitt. Enter Davis, who promptly struck out the last five batters of the game. "I've never even struck out five batters in a game before," Davis said.

While everyone (48,592 paid) was asking the question, Where's Gossage? Davis struck out pinch-hitter Dave Revering on three pitches and Rickey Henderson on four.

In the top of the 10th, Mumphrey, the other new Yankee outfielder from San Diego, hit his third home run of the season (he had three in 1980), to put the Yankees ahead, 3-2.

Then Davis continued his Gossage impersonation, striking out Dwayne Murphy, Cliff Johnson and Tony Armas to end the game. Gossage stopped warming up in the bullpen, watching in appreciation.

"We (the rest of the bullpen) don't get too much credit," said Davis, who had 16 strikeouts in 11 2/3 innings coming into the game. "We don't expect too much. I guarantee you they would rather have struck out against me than Gossage. He's frightening."

In the second game, they got their chance. Jim Spencer put the Yankees ahead, 1-0, in the seventh with his first home run of the season.

In the eight, Dave Winfield, the richest man in baseball, got one of the game's cheapest hits, a checked swing RBI single that landed just short of the right field grass. "I can't believe he makes $20 million and hits the ball that softly," said A's Manager Billy Martin. "They say he's a decent hitter, but I haven't seen it. He has the softest bat I've ever seen for a guy 6 foot 6. I think George (Steinbrenner) has lost his feathers."

In the ninth, John, who gave up only five singles while winning his fourth game of the season, began the inning by walking Murphy. This time, there was no doubt as to who was coming out of the bullpen: Gossage, who had not pitched since Monday.

He struck out Cliff Johnson, before giving up a self-defense single to Armas. Gossage throws so hard, you'd think the ball would unravel before it got to home plate. But it was the A's that unraveled. Mike Heath and Wayne Gross went down swinging.

"In the fifth or sixth, I start thinking about it," Gossage said. I start stirring. When the phone rings, I start to stir a little more. If the starter gets in trouble, I know it's gonna be my territory. By the time I reach the mound, I'm ready.

"Since I was 7 years old, I could bring it. It's always been this way. I was always overpowering. When I was very young, I was skin and bones. My brother and I would have a catch in the front yard, and he would say, 'You can't throw hard.' I would get tears in my eyes and be throwing and crying. Maybe that's where I got it from."