SAN FRANCISCO -- The way his season started in the batter's box, Max Muncy realized he had to find a rhythm again. He had abandoned his step back move with the left leg in a remake of his mechanics. But, suddenly, he was thinking too much, chasing pitches and struggling to correctly recognize what pitchers were throwing his way.

Anxiety hit hard as the Los Angeles Dodgers slugger began 1-for-16, then 4-for-33 as he studied film and made tweaks -- until everything finally felt right again Monday night. And the tried-and-true move with his left leg, he brought that back, too.

Muncy hit a grand slam and a three-run drive for his 10th career multihomer game, Mookie Betts led off the game with a homer and Los Angeles rediscovered its power game in a 9-1 win over the San Francisco Giants.

"It was kind of one of those things where tough first game of the season got me into a mental rut and my mechanics got out of whack. This was just an easy solution to fix things," Muncy said. "... I had a lot of tough pitching to start and I was getting out of my mechanics. This is one of those things where it kind of takes it out of my head."

Muncy hit his third career grand slam and first since July 1, 2021, against Washington. His seven RBIs were a career high with his previous best of five done three times, the last on June 9, 2022.

Manager Dave Roberts already planned to rest Muncy on Tuesday -- if a player hits three home runs Roberts reconsiders any plan about resting someone.

Muncy has 23 home runs and 51 RBIs in 73 games against the Giants.

"It's a lot of fun," he said. "Success in general is fun. But it does a little bit more for me when it's here."

Julio Urías (3-0) struck out eight, walked two and allowed one run on four hits over six innings. The star lefty received plenty of run support from a lineup that had homered in each of the first nine games before missing during Sunday's 11-6 loss at Arizona.

Wilmer Flores homered leading off the fourth for San Francisco. That ended 13 scoreless innings tossed by Urías since he surrendered two runs on three hits in his initial three innings on opening day against the Diamondbacks.

"Julio set tone for tonight. I thought you could see it with his emotion, his energy," Roberts said.

Giants ace Logan Webb (0-3) struck out six over six innings but remained winless in a tough start to the year as the Giants played their first matchup against a National League team after facing the AL in the first eight games.

The Dodgers ended a three-game losing streak in which they gave up 29 runs in the last three matchups of a four-game series at Arizona that Roberts chalked up to not pitching well.

Freddie Freeman singled in the third for a five-game hitting streak, while Betts added a pair of singles to his second home run of the year.

Los Angeles has won nine of the last 10 NL West crowns, including eight straight before the 107-win Giants edged the 106-win Dodgers on the season's final day of 2021. The Dodgers have also now won 14 of their last 15 games against the Giants, outscoring them 92-42 (+50). It's the first time since the teams moved to California in 1958 that one team has beaten the other 14 times in a 15-game span.

Muncy is the third Dodgers player with three or more multihomer games against the Giants, joining Roy Campanella and Gil Hodges, and has the Dodgers' most multihomer games against the Giants since the franchise moved to Los Angeles.

Before he started clearing the fences Monday, Muncy drew a two-out walk in the first to reach base safely in a 27th straight game in San Francisco -- the third-longest streak doing so by a visiting player behind teammate Freeman's 31 and Wil Myers (28).

J.D. Davis had two hits for San Francisco to begin a tough series when it will face two left-handed starters -- with Clayton Kershaw pitching Wednesday's series finale.

ESPN Stats & Information and The Associated Press contributed to this report.