CHICAGO -- Giants manager Bruce Bochy stuck with the percentages Sunday in his choice of first basemen, opting for right-handed-hitting Brett Pill instead of left-handed-swinging Brandon Belt, San Francisco's primary starter at that spot.

Left-hander Travis Wood, Chicago's starting pitcher, entered the game having limited left-handed batters to a .196 average, compared with .255 against right-handers. But Pill hadn't taken full advantage of his opportunities against lefties, as his .214 batting average against them demonstrated. Belt had hit .232 off lefties.

Belt also entered Sunday batting .349 in his last 27 games, lifting his overall average to .266. Bochy expressed confidence that Belt, a .225 hitter last year, will continue to progress.

"He's made some adjustments that will help him. His confidence has grown, too," Bochy said of Belt, who has been in and out of the lineup this year instead of back and forth between San Francisco and Triple-A Fresno, as was the case last season. "It's the usual growth year for a young player. He's turning on the ball yet using the whole field."

Injury problems may be behind Sandoval's struggles

CHICAGO -- The Giants' success has obscured Pablo Sandoval's lack of production.

Expected to provide power, Sandoval owned eight home runs in 329 plate appearances entering Sunday, compared to 23 homers in 466 plate appearances last year. He hadn't homered since July 8 at Pittsburgh off A.J. Burnett.

Of course, Sandoval shouldn't be singled out. The Giants entered their series finale against the Chicago Cubs with 81 homers, safely ranking last in the Major Leagues.

Manager Bruce Bochy attributed Sandoval's diminished pop to his injuries. His fractured left hamate bone and a strained left hamstring forced him to miss a total of 53 games, disrupting his continuity. "His timing was off a little bit," Bochy said.

Bochy indicated that Sandoval's weight, a perpetual issue, could be affecting his hitting. Without citing a specific figure, Bochy said that the Giants are "happy" with Sandoval's weight, but added, "I won't lie to you. We'd like to get him down a little bit."

Bochy said that Sandoval's weight "is something he's been battling," adding, "He showed last year he's a different hitter when his weight is down."

Sandoval hit .315 with a .552 slugging percentage and a .909 OPS (on-base plus slugging percentage) a year ago, compared with corresponding figures of .281, .444 and .778 entering Sunday.