PHOENIX -- Brock Stewart saw his opportunity and seized it.

The Los Angeles Dodgers' rookie pitcher, replacing Bud Norris as Saturday's starting pitcher, threw five solid innings and got a boost from a two-run homer by Joc Pederson as the Los Angeles Dodgers rolled to a 6-2 win over the Arizona Diamondbacks.

"It starts with Brock," manager Dave Roberts said. "We let him know yesterday he was going to start. For a young player to adjust and be ready to pitch in a major league ballgame and get guys out says a lot about him."

Stewart has had a meteoric rise in the Dodgers' ranks this season, starting at Class A Ranch Cucamonga. In fact, he is the first Dodger since Hideo Nomo in 1995 to start in Single A and start an MLB game in the same season.

After making his fifth MLB start, Stewart said, ""It's definitely something I don't take lightly. I'm very happy they're giving me these opportunities. I'm glad it's been working out lately."

Roberts praised another rookie, Andrew Toles, for throwing out a runner at the plate to cut off a Diamondbacks' rally. "A huge play."

Overall, "A well-played baseball game," Roberts said.

"I really like where we're at. We're playing some good baseball."

With San Francisco losing Saturday night, the Dodgers (84-64) reduced their magic number to 10 to clinch their fourth straight NL West title.

Stewart (2-2) allowed two runs in five innings, striking out six and walking one. He allowed home runs to red-hot Jean Segura and Welington Castillo.

Five Dodgers relievers blanked the Diamondbacks (62-86) over the final four innings.

Miller (2-12) allowed four runs and seven hits in 5 1/3 innings, ballooning his ERA to 7.10.

Corey Seager picked up two hits to bring his season total to 181, most by a Dodgers' rookie. Steve Sax had 180 in 1982.

"It's very impressive, obviously with all the rookies of the year that we've had in the Dodger organization," Roberts said. "No surprise. I think there's going to be Dodgers' records I foresee from Corey."

Segura, who also singled, needs 14 hits to reach 200 for the season. He is 12-for-23 with five homers in his last five games.

"Just got to keep him hot," D-Backs manager Chip Hale said.

The Dodgers, though, shut down the three hitters after lead-off man Segura as Chris Owings, Paul Goldschmidt and Jake Lamb combined to go 0-for-12.

Los Angeles is 5-4 on its season-long 10-game road trip, which ends Sunday in Phoenix.

The Dodgers opened the scoring off Shelby Miller, the Diamondbacks' beleaguered starter, with a triple by Seager that rattled around in the right-field corner and a sacrifice fly by Justin Turner.

Segura led off the bottom of the first by belting his seventh leadoff homer of the season -- just inside the left-field foul pole -- to tie the game.

Miller came unglued in the fourth.

He walked Adrian Gonzalez and Josh Reddick blooped a single to center. Castillo was charged with a passed ball and after picking up the ball made a throwing error to third allowing Gonzalez to score with Reddick taking third.

Pederson launched his monstrous blast way over the pool in right-center, to give the Dodgers a 4-1 lead.

"There was a guy on third with less than two outs," Pederson said. "So I was going whatever I can to get him in."

Miller said he thought he made a good pitch on Pederson. "It was down and in. Right where I was trying to hit my spot and he just basically got a good swing on it.

"I thought I made some good pitches. Kind of got into some tough situations. Kind of just had one bad inning and it kind of got carried away there ... tough outing."

Castillo's homer to left to cut the Dodgers' lead to 4-2 in the fourth. The Diamondbacks put runners on first and second with two out, and Mitch Haniger singled to left, but Dodgers left fielder Andrew Toles easily threw out Yasmany Tomas trying to score from second.

Los Angeles added an insurance run in the seventh when Chase Utley hit a run-scoring double and another in the ninth when Seager singled and came around to score on a wild pitch.

NOTES: The Dodgers roared their approval in the clubhouse when they saw the Giants blow a 9th-inning lead to St. Louis...Dodgers catcher Yasmani Grandal has a sore right elbow, so manager Dave Roberts gave him Saturday off. "It's something that's kind of been bothering him for a while," Roberts said. ... Dodgers third baseman Justin Turner had established career highs in games (138), runs (70), hits (137), doubles (31), home runs (27), RBIs (84) and walks (44). He leads the Dodgers and is No. 3 in the NL with 28 go-ahead RBIs this season. ... Saturday marked the 20th anniversary of Hideo Nomo's first no-hitter, a 9-0 victory at Colorado. ... Diamondbacks catcher Oscar Hernandez flew in from Venezuela and was activated, giving Arizona three catchers (Wellington Castillo, Tuffy Gosewich) to finish the season. Backup Chris Herrmann is injured and out for the year. Castillo missed a game recently because of a sore quad so the D-Backs didn't want to be caught short-handed. ... D-backs outfielder A.J. Pollock, out with a groin injury, is making continued improvement and may rejoin the D-Backs before season's end. "At the earliest, maybe in Washington (Sept. 26)," manager Chip Hale said.