AP Sports Writer
SAN DIEGO (AP) -- The San Francisco Giants are on their first winning streak in nearly three weeks thanks to Buster Posey's season-high five RBIs and Jose Mijares' lights-out relief.
The Giants beat the San Diego Padres 10-1 Friday night to win consecutive games for the first time since they beat San Diego June 18-19 at San Francisco. Coming in, the defending World Series champions had lost 16 of 20.
Marco Scutaro and Brandon Crawford had three hits apiece and Gregor Blanco scored four times in San Francisco's highest-scoring game since it beat Pittsburgh 10-0 on June 13.
The performance of the game, though, belonged to Mijares.
The Padres were trailing 5-1 when they chased Chad Gaudin by loading the bases on a single and consecutive walks with no outs in the sixth. But the lefty Mijares came on and retired the side on eight pitches. He got lefty Yonder Alonso to pop up to shortstop before striking out Jedd Gyorko and pinch hitter Chris Denorfia.
"Player of the game right there," Gaudin said. "It's something else."
Said Mijares: "I'm ready for every pitch. I'm ready for the lefty. That's it."
Mijares said he wasn't necessarily surprised that manager Bruce Bochy left him in to face the right-handed Gyorko after he retired Alonso.
"I'm ready for everything. I'm ready for the righty, lefty," he said.
"That's a huge part of the game," Padres manager Bud Black said. "The last two weeks we have not really gotten that real big hit to swing momentum to our side."
Gaudin and three relievers combined on a five-hitter.
The Padres lost for the 17th time in 20 games and dropped a season-high 12 games under .500.
Posey's two-run double highlighted San Francisco's five-run seventh inning, when Black was thrown out.
Black was ejected by second base umpire Laz Diaz for arguing after Kensuke Tanaka was awarded third base on an obstruction call against third baseman Chase Headley. Tanaka was on the infield grass when he and Headley collided.
"The definition of obstruction is when you're not in possession of the ball and when you're not fielding the ball, you hinder the process of the runner," crew chief Mike Winters said. "He's throwing the ball, so he's neither of those two things apply to him. He basically has to disappear at that moment. It was a textbook obstruction case and Laz ruled it exactly, 100 percent correctly."
The Giants led 5-1 going into the seventh, when Brad Brach allowed five runs on five hits and a walk. Because of the obstruction call, four of the five runs were unearned. Scutaro and pinch hitter Andres Torres had RBI singles and another run scored on a wild pitch.
Posey also had a sacrifice fly in the third and a two-run single in the sixth.
Gaudin (3-1) improved to 3-0 with a 2.70 ERA in six starts since joining the rotation on June 2. He allowed one run and three hits, struck out five and walked four.
Sean O'Sullivan (0-1) lost his debut with his hometown Padres. He threw 102 pitches in five innings, allowing two runs and six hits. He also doubled leading off the third.
O'Sullivan, who graduated from Valhalla High in suburban El Cajon in 2005, signed a minor league deal in December.
NOTES: The Padres made several moves before the game, including moving LHP Clayton Richard to the 60-day DL and announcing he will have season-ending surgery on his pitching shoulder. Also, 1B Yonder Alonso and 2B Jedd Gyorko were activated from the 15-day DL, INF-OF Kyle Blanks was placed on the 15-day DL with left Achilles tendinitis, RHP Miles Mikolas was optioned to Triple-A Tucson and SS Pedro Ciriaco was designated for assignment. ... The four-game series continues Saturday night when Giants RHP Tim Lincecum (4-9, 4.61 ERA) faces RHP Edinson Volquez (6-7, 5.33 ERA).
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.