CHICAGO -- Clutch situations are prime time for Addison Russell.

The Cubs shortstop hit a two-run, seventh-inning single with bases loaded to give Chicago a lead it never relinquished in a 5-4 victory over the San Francisco Giants on Thursday night.

"It's definitely a lot of fun," said Russell, who drove in Dexter Fowler and Kris Bryant with what proved to be the tying and game-winning runs off Giants reliever Cory Gearrin. "I kind of embrace the situations. In that situation, I really didn't try to do too much, just wanted to see a pitch."

It was Russell's 11th game-winning RBI of the season, 10 of which have come at Wrigley Field. He is 8-for-18 (.444) with 23 RBIs with the bases loaded.

The Cubs (86-47) captured their fourth consecutive game, improved to a season-high 39 games over .500 and extended their National League Central lead to 15 1/2 games.

Chicago reliever Joe Smith (1-0) worked two perfect innings for the victory, secured just hours after he was activated from the disabled list. Giants reliever Hunter Strickland (3-2) took the loss after he put tying and go-ahead runners on base.

Cubs reliever Carl Edwards Jr. pitched a one-two-three ninth for his first career save.

Chicago starter Mike Montgomery worked four innings and didn't factor in the decision. Nor did Giants right-hander Jeff Samardzija, who was knocked around early in his first career start against the Cubs at Wrigley Field.

The Giants (72-61) fell two games behind the idle NL West-leading Los Angeles Dodgers. They remain atop a tight pack in the NL wild card chase, 1 1/2 games in front of the St. Louis Cardinals, who hold the final playoff position.

San Francisco managed only three hits, just one after the opening inning.

"We played well considering we had three hits," said Giants manager Bruce Bochy. "We had some good at-bats early, but we just got shut down after the third inning there. We couldn't generate anything offensively."

Samardzija, who pitched for the Cubs from 2008-14, gave up three first-inning runs and then settled down through his pitch-heavy, four-inning effort.

Trailing 4-3, the Cubs loaded the bases in the seventh against Strickland and Will Smith, who got Jason Heyward to pop out to right for the second out. Gearrin came in to face Russell, who laced an 0-1 pitch to left.

Hunter Pence gave the Giants a 2-0 lead in the first inning with his two-out home run deep into the left field bleachers. His ninth homer of the year came on a 1-0 pitch and scored Denard Span, who led off the game with a double to right.

The Cubs replied with three runs on four hits while Samardzija threw 47 first-inning pitches.

Bryant extended his hitting streak to 14 games with a bloop single to right that scored Fowler. Heyward followed with a single to left-center to plate Anthony Rizzo, and Chris Coghlan's two-out double to right brought home Ben Zobrist.

Samardzija said he is enjoying the Cubs' success from afar even if he didn't fare as well as he would have liked on Thursday.

"Being a Chicago guy, I always like it when Chicago teams do well," he said. "It's always good to see good baseball being played in the summer and into the fall. They're playing well. It's fun to see. It's a great venue and a great place to see a ballgame."

Samardzija's second-inning sacrifice scored Joe Panik to forge a 3-3 tie. In the third, Brandon Crawford grounded into a fielder's choice for a 4-3 San Francisco lead as he brought home Buster Posey.

Montgomery allowed four runs -- three earned -- on three hits while striking out one and walking three in a four-inning outing.

Samardzija left shortly after. He also worked four innings, giving up three runs on three hits. He walked three and struck out three while throwing 87 pitches.

NOTES: The Giants opened a 10-game road trip that includes stops in Colorado and Arizona. ... San Francisco made six moves prior to Thursday's game as rosters expanded, including reinstating LHP John Osich (left forearm strain) and OF Mac Williamson (left shoulder strain) from the 15-day disabled list. LHP Ty Blach, LHP Matt Reynolds, LHP Steven Okert and INF Kelby Tomlinson were recalled from Triple-A Sacramento. ... San Francisco sends RHP Albert Suarez (3-2, 4.35 ERA) against Cubs LHP Jon Lester (14-4, 2.70 ERA) in Friday's second game of the series. ... The Cubs announced three transactions prior to Thursday's game, including the activation of OF Chris Coghlan (right rib contusion) and RHP Joe Smith (left hamstring strain) from the DL. Chicago called up RHP Jake Buchanan from Triple-A Iowa. ... The series is the second meeting this season between the teams. The Giants took two of three at AT&T Park May 20-22.