PHOENIX -- Before Saturday's game, Dodgers manager Don Mattingly said veteran shortstop Jimmy Rollins would get his starting job when he returns from a finger injury.
Corey Seager is doing his best to make that decision a little more difficult.
Seager, called up Sept. 3 from Triple-A, went 4 for 4 including his first major-league home run to lead Los Angeles to a 9-5 win over the Arizona Diamondbacks. He also finished with three RBIs, scored three times and stole a base.
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Joc Pederson, Adrian Gonzalez and Carl Crawford also homered for the NL West-leading Dodgers.
"You've got a lot of veterans around that help and kind of guide you through the days and let you know what you need to do and be where, and it makes it a lot easier that way," Seager said.
Seager, 21, has reached base in eight straight plate appearances. He has hit safely in all eight of his major-league starts while batting .467 (14 for 30).
"When you're going good you're always confident. You're relaxed. Everything's clicking. It's been a good run so far," Seager said.
"He doesn't have to do anything more," Dodgers manager Don Mattingly said. "He's been good. He just has good at-bats. He's been putting quality at-bats together."
Seager got help from a Diamondbacks fan who reached over the padding down the left-field line in the fifth inning to take a seemingly catchable foul ball away from David Peralta and Jake Lamb. Seager then homered in the same at-bat and another fan returned the ball to him.
Seager said he owed the first fan a thank you, too. Peralta was far less pleased.
"I was hustling all the way, trying to make the play," Peralta said. "I was under the ball and the fan just put his glove over mine. I got (mad). Then you see what happened, the next pitch he hit a home run."
J.P. Howell (6-1), the first of seven Dodgers relievers, got the last out in Arizona's three-run fourth to pick up the win.
Rubby De La Rosa (12-8) gave up six runs and nine hits in two-plus innings to fall to 0-3 against the Dodgers this season.
Crawford began the game with his ninth career leadoff home run, a line drive just over the right-field fence. Then Chase Utley singled, took third on a two-out single by Andre Ethier and scored on a soft ground ball to second base from Seager that the Diamondbacks' Chris Owings juggled for a hit.
That gave the Dodgers a 2-0 lead in the first inning, and they went ahead 7-0 in the third on Gonzalez's leadoff home run, Ethier's run-scoring double, an RBI single for Seager and Pederson's two-run blast.
The Diamondbacks rallied for three runs in the bottom of the fourth and loaded the bases with two out, after Peter O'Brien's pinch RBI single and sacrifice flies for Nick Ahmed and Ender Inciarte.
Mike Bolsinger had thrown a wild pitch earlier in the inning to put runners in scoring position. He was replaced by Howell after an intentional walk to Paul Goldschmidt, and Howell got Peralta to fly out to shallow left field to end the threat.
Seager made it 8-3 with his home run, and Inciarte cut the lead to 8-4 in the sixth with a single to drive in A.J. Pollock.
Peralta's 15th home run of the season, off the Dodgers' Luis Avilan, came in the seventh and Alex Guerrero added an RBI double in the ninth.
De La Rosa brushed back Seager with an inside pitch in the third, just before Seager singled up the middle. Both teams were warned by home plate umpire Brian O'Nora.
O'Nora joined the umpiring crew for the series in time for Saturday's game and worked home plate, with Jim Wolf out after being struck in the mask by a foul ball during the second inning on Friday night.
GAME TIME CHANGE
The Diamondbacks' regular-season finale on Oct. 4 against the Houston Astros has been changed from a 1:10 p.m. start time to 12:10 p.m, local time.
Dodgers: Zack Greinke (16-3, 1.68 ERA) is 8-2 in 13 road starts this season. He is 6-3 with a 3.62 ERA against Arizona in his career (13 starts), including a 5-2 mark at Chase Field.
Diamondbacks: LHP Patrick Corbin is 2-0 in his last three starts and 3-2 with a 3.82 ERA in six career starts against the Dodgers.