Troncoso wriggled out of a bases-loaded jam in the ninth after Randy Wolf pitched impressively into the eighth inning, helping Los Angeles beat the Chicago Cubs 2-1 on Thursday for its fourth straight victory.
Juan Pierre had two hits and scored a run for the Dodgers, who have the best record in baseball at 34-15.
The Cubs have lost nine of 11, and learned earlier in the day their ace Carlos Zambrano was suspended six games for his tirade during Wednesday's victory over the Pittsburgh Pirates. Zambrano said he won't appeal the penalty, which included a fine. Barring rainouts, he is eligible to return next Thursday.
Wolf (3-1) allowed one run and six hits. He struck out seven and walked one.
Troncoso pitched the ninth after Torre let him bat in the top of the inning. Torre wanted to give Jonathan Broxton the night off after he walked three in Wednesday's win at Colorado.
"Troncoso was amazing, got on that high wire and then just wiggled himself off. It was terrific," Torre said. "He's either scared or in control. I'm not worried about him anymore in those situations."
After watching his team blow scoring opportunities in the eighth and ninth, Cubs manager Lou Piniella declined to talk to the media after the game.
"You feel like we had some good chances late in the game," Reed Johnson said. "Runners on first and second twice with nobody out in the eighth and ninth inning and we feel like you got to feel confident coming out of those two situations with at least one run and we were not able to do it."
Reminiscent of last year's three-game sweep of the Cubs in the division series, the Dodgers got a strong outing from their starter. Wolf kept Chicago in check with his breaking pitches. After giving up a leadoff single in the fifth, he struck out the side.
"I finally had my fastball velocity back, couple of starts I was down a little bit, but I felt a lot stronger today," Wolf said.
Wolf's lone mistake came in the eighth, when Scales went deep on a 3-2 pitch. He was replaced by Troncoso.
"After he gave up the home run there was no way I was going to give him a chance to lose that game," Torre said. "That's for sure. He pitched well."
Scales was optioned to Triple-A Iowa on Wednesday, but was recalled before the game when Ryan Freel went on the disabled list with a left hamstring strain. It was the second pinch-hit homer of the season for the 31-year-old rookie.
Troncoso gave up two hits in the eighth but got out of the inning with help from a double-play grounder.
Pierre led off the game with a single and stole second. Rafael Furcal then laid down a bunt that was out of the reach of third baseman Mike Fontenot. The ball rolled to the outfield grass and Pierre scored from second.
Furcal scored on Casey Blake's groundout in the third inning. Furcal was back in the starting lineup after missing four games with pain in his left buttock.
Randy Wells (0-2) pitched seven strong innings for the Cubs in his fourth career start, allowing two runs and eight hits. The right-hander is winless despite a 1.80 ERA.
"We just missed opportunities to score," Wells said. "It was a good baseball game."
Dodgers second baseman Orlando Hudson had his 17-game hitting steak snapped.
- After the game, the Dodgers placed LHP Will Ohman on the disabled list with a sore shoulder and recalled C A.J. Ellis from Triple-A Albuquerque.
- Torre said there are no definitive plans for suspended OF Manny Ramirez when they get back to Los Angeles on Monday. "No, but I am assuming we will see him at some point," Torre said.
- RHP Hiroki Kuroda, on the DL with a left oblique strain, allowed seven runs and nine hits over five innings in a rehab assignment with Class A Inland on Wednesday. Torre said the club will make a decision on Kuroda's status after he throws a bullpen session on Friday.
- Cubs RHP Ted Lilly, who was ejected after arguing with umpire Bob Davidson from the dugout in Monday's win over the Pirates, was fined $1,500.