SAN FRANCISCO -- Travis Wood was such a powerful force Sunday, even his shadow contributed to a Chicago Cubs win.
With Wood watching from the on-deck circle, San Francisco Giants starting pitcher Tim Lincecum chose to challenge No. 8 hitter Welington Castillo with a 3-1 fastball, rather than tread cautiously and go after the opposing pitcher.
That's what happens when the opposing pitcher has already homered and is the major league leader in home runs among pitchers.
Wood held the Giants to four hits in seven innings and helped his own cause with a home run, and batterymate Castillo broke a seventh-inning tie with a solo shot as the Cubs completed a three-game sweep of the defending champions with a 2-1 victory.
Chicago finished a 6-4 Western trip by wrapping up its first series sweep in San Francisco since September 1993. The Cubs began the trip by going 1-2 at Colorado and 2-2 at Arizona.
"I can't ever remember playing that well on the West Coast," said Cubs manager Dale Sveum, who was including his 14-year playing career. "To win six of 10 after making a couple of trades ... somehow we pitched well enough."
Following in the footsteps of Edwin Jackson and Chris Rusin, Wood (7-7) turned in his 18th quality start in 21 outings. The Cubs' lone All-Star representative walked four and struck out seven. The only run he allowed was unearned.
The left-hander admitted the last thing he was thinking as he prepared to bat in a 1-1 tie was that Castillo, who had two homers in the Cubs' first 102 games, would turn the game in Chicago's favor with a solo act.
"I was hoping for the best for Welly," Wood said. "I've gotta say, I wasn't thinking homer, but I feel good for him."
Castillo said he expected Lincecum (5-11) to challenge him.
"I was ahead in the count. I was thinking fastball. I was ready for it," he said of his first home run since June 20. "I put my best swing on it. I hit it and we win."
Pedro Strop pitched a scoreless eighth inning before turning the ball over to closer Kevin Gregg, who recorded his third save in three days and 22nd of the season. The Cubs (48-55) improved to 33-27 outside the National League Central.
Meanwhile, the defeat saddled the Giants with a four-game losing streak as they prepared to fly cross-country for Monday's annual champions' visit to the White House. It will be the Giants' second up-close-and-personal with President Barack Obama in the past three years.
Lincecum, two starts removed from a no-hitter in San Diego on July 13, allowed only four hits in seven innings. However, he fell victim to the two home runs, the 14th and 15th he's allowed this season, including five in his past two games.
Wood's fifth-inning homer, the first ever allowed by Lincecum to a pitcher, didn't catch the former two-time Cy Young Award winner by surprise.
"It's rare that you find a pitcher who can hit like that," Lincecum said. "Guys like him and (Cincinnati's Mike Leake, who had three hits against the Giants earlier in the week), you know they can really handle the bat."
Lincecum walked two and struck out 10, his third double-digit strikeout effort of the season and the 36th of his career.
Wood's home run came with two outs and two strikes in a scoreless game in the top of the fifth. The homer was his third of the season, and the RBI was his eighth, tied with former teammate Scott Feldman for the major league high by a pitcher.
"I'm always trying to help myself," said Wood, who also singled while raising his average to .293. "I was fortunate enough to get two hits today, and one went out of the park."
San Francisco pulled even in the bottom of the fifth. Lincecum singled off Wood, his first of two hits, and eventually got tagged out at the plate on a double-play grounder by Buster Posey. However, Pablo Sandoval followed with an RBI double to left field to score Marco Scutaro.
The Giants, who began the day having recorded two or fewer hits with runners in scoring position in 26 of their previous 32 contests, went 2-for-8 under those circumstances, with Hunter Pence three times ending innings with two teammates on base.
Fittingly, the game ended when pinch hitter Gregor Blanco popped out to shortstop one pitch after Kensuke Tanaka stole second base and took third on a throwing error by Castillo.
NOTES: Only one other pitcher -- Milwaukee's RHP Yovani Gallardo -- has hit more than one home run this season. Gallardo has two. ... The last-place Giants (46-58) fell to a season-worst 12 games under .500. ... Giants 1B Brandon Belt, whose two-out, ninth-inning error allowed the tying and winning runs to score for the Cubs in Chicago's 3-2 win Friday, went 0-for-4 with four strikeouts Sunday. ... While the Giants are visiting the White House, the Cubs will be opening a seven-day, eight-game homestand Monday. Rookie sensation Junior Lake, who began his major league career with a seven-game hitting streak in Colorado and Arizona before going 0-for-12 against the Giants, is expected to make his Wrigley Field debut in the opener of a four-game series against Milwaukee. ... Neither team took batting practice before the game, but that didn't stop the Cubs from cheering a morning home run. Many Chicago players were watching on television in the clubhouse when former teammate Alfonso Soriano belted his first homer for the New York Yankees. ... After the game, the Giants announced they had activated RHP Guillermo Moscoso, who was acquired Friday in a trade with the Cubs, and designated RHP Yusmeiro Petit for assignment.