SAN FRANCISCO — Buster Posey awakened Saturday morning in Salt Lake City, caught a flight to San Francisco, rescued a kitten from a tree, helped an old lady across the street and donated two pints of blood.

Well, not really. But honest to goodness, the stoic rookie with the Eagle Scout looks did arrive at AT&T Park. And gosh darn if he wasn't worth the wait.

Hours after the Giants recalled Posey, their brightest hitting prospect in two decades, he delivered three times in RBI situations and sparked the club to a 12-1 victory over the Arizona Diamondbacks.

To a series of standing ovations at AT&T Park, the new No. 6 hitter lined a run-scoring single in the first inning for his first major league RBI. He shot another RBI single up the middle in the fifth. And he grounded a single through the left side with the bases loaded in the seventh.

Then he stood on first base, finally cracking a smile.

"It was great. It was fun. It's humbling," said Posey, asked about the crowd's embrace. "That's the time I have to slow myself down because it can get you going a little bit."

Juan Uribe and Eli Whiteside hit home runs to back Jonathan Sanchez as the Giants romped to their largest margin of victory this season.

Posey, 23, was batting .349 at Triple-A Fresno, and Giants officials finally indulged the pleas to promote him, deciding they had a window of opportunity at first base while Mark DeRosa and Edgar Renteria are on the disabled list.

Manager Bruce Bochy said Posey remains the Giants' catcher of the future, but he will receive nearly all his playing time at first base for however long this stint lasts.

"It makes sense until we get all our guys back," Bochy said. "Then we'll see where we're at."

Translation: Posey could return to Fresno within two weeks. But if he keeps having three-hit nights, don't bet on it.

Everyone expects so much of Posey. But what does he expect of himself?

"I just expect myself to work hard every day, and when the games come around, try and contribute and help this team get wins, hopefully," he said before the game. "There's a lot of good hitters on this team. I don't feel I have to do extraordinary things to help the team get wins."

Maybe his season debut wasn't extraordinary. Just uncommonly good.

"He takes good approaches up there," said Aubrey Huff, who moved to left field to free up first base for Posey. "I saw it in spring training. He lets the ball travel, lets it get deep, and he has good at-bats. He's got a great head on his shoulders. He stays back so well. He keeps the bat head behind the ball.

"Even that curveball down. He kind of chased it, but hit it back up the middle. That was impressive. Bases loaded and nobody out, a lot of guys try to do too much. He got a nice, easy single and kept the line moving."

Uribe hit in front of Posey and ensured the rookie would have plenty of RBI chances. He reached base four times and scored three runs. Pablo Sandoval had his first three-hit game since April 25, too.

Posey learned of his promotion at 11:30 p.m. Friday from Fresno manager Steve Decker, who called his hotel room. Posey got on a plane Saturday morning and said he had a little trouble sleeping.

"There's a few butterflies," he said.

They fluttered away quickly. Posey's single in the first capped a two-run rally, which had to be a relief for Sanchez. The left-hander took the mound having received zero run support in five of his previous nine outings.

Sanchez gave back a run in the third when Rusty Ryal hit a home run. But Uribe matched it with his solo shot in the bottom of the inning, Sanchez allowed two hits and four walks over five innings, and the bullpen threw four hitless innings.

Combined with Matt Cain's shutout the previous night, the Giants have yielded just three hits to Arizona in two games while positioning themselves for a series sweep.