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LOS ANGELES -- It was hard to tell who needed the shot of confidence more -- Russell Martin or the Los Angeles Dodgers.

They both benefited when his grand slam snapped a sixth-inning tie, propelling the Dodgers to a 7-2 victory over the Chicago Cubs on Thursday night in the series opener.

"It was big for us. Russell Martin needed that," manager Joe Torre said. "It broke open a tie game and just gave Russell something to go on. We all pull for each other. They know when guys are struggling and trying to find it. The fact that Russell hit it really elevated everybody's mood."

Martin has been searching for some offense all month to no avail, hitting just .246. He went 0 for 3 against St. Louis a night earlier and hadn't homered since July 26 against Florida. He has just four homers this season.

"There's nothing I can change in the past. I haven't had a great season so far," he said. "Hopefully, this ignites a little fire within me. We haven't been playing our best baseball lately. We believe in what we have here. It just takes a few guys to step up."

Martin launched the first pitch he saw from Angel Guzman (2-3) just over the left-field fence, breaking a 2-all tie and earning the catcher a curtain call.

"I put a good swing on the ball, really just trying to get one run in," he said. "I haven't trotted around the bases very often this year. It's only my second home run at home."

Martin's second career grand slam provided some much-needed offense for the struggling Dodgers, who had scored three runs or less in five of their previous seven games. They'd lost each of those five games and saw their NL West lead shrink to 3 1/2 games over Colorado in that stretch.

"We need to string something together," Torre said. "We've been back-and-forth with this thing."

Los Angeles still owns the NL's best record at 72-50, although the club is just 16-18 since the All-Star break, including an 8-11 mark this month.

The Cubs have their own problems, going 4-10 in their last 14 games to drop seven games behind NL Central-leading St. Louis.

"That's what happens when you don't score runs," Aramis Ramirez said. "We had the pitching, but we didn't hit with men in scoring position. I can't figure it out because we've got guys in here who can do better than what we're doing right now. We've got talent. We just can't get it done."

Ronald Belisario (2-2) got two outs for his first victory since April 30. He walked one five days after coming off the 15-day DL.

Jeff Weaver made a spot start in place of right-hander Hiroki Kuroda, who is on the 15-day DL with a concussion after being hit in the head by a line drive last weekend in Arizona. The right-hander gave up two runs and five hits in 5 1/3 innings, struck out four and walked two.

Guzman took the loss, yielding four runs and three hits in one inning, while striking out one and walking one.

"I was trying to be aggressive in the strike zone and trying to get a groundball. It didn't happen, but I don't think I'm going to change my approach to the hitters," he said. "I'm going to try to stay aggressive, the way I've been doing it the entire year. Two bad outings won't bring me down."

Tom Gorzelanny got off to a rocky start for the Cubs, giving up three hits and a run to the first four batters he faced and committing an error. Chicago rallied twice to tie the game before Martin's grand slam put it out of reach.

"That was pretty big," said Matt Kemp, who went 2 for 4. "We needed that and Russ needed that. He's been hitting the ball pretty hard the last few weeks right at people."

Casey Blake's RBI single extended the Dodgers' lead to 7-2 in the seventh. Manny Ramirez went 3 for 4 coming off a hitless night against the Cardinals on Wednesday.

The Dodgers took a 2-1 lead in the second on Rafael Furcal's RBI single with two outs. Their first run came on Andre Ethier's fielder's choice in the first.

Kosuke Fukudome, who went 3 for 3 with a walk, tied the game at 1 on his career-high 11th homer in the second. The Cubs tied the game in the third on a single by Aramis Ramirez. They loaded the bases but Alfonso Soriano and Jeff Baker struck out to end the inning.

Game notes

Kuroda is eligible to return on Aug. 31, the start of a four-game series against Arizona. ... The Dodgers improved to 1,015-1,014 all-time against the Cubs. ... Martin's first grand slam came on April 27, 2007, against Pittsburgh at home. ... Penny Marshall was a pregame dugout visitor with Dodgers manager Joe Torre. Chicago native Jim Belushi got booed when he was spotted wearing a Cubs cap.