PHILADELPHIA -- First, Kyle Schwarber did what he often does in the playoffs.

Then, Bryce Harper did what he's always wanted to do on his birthday.

Schwarber led off Game 1 of the National League Championship Series with a first-pitch homer Monday night, and Harper, celebrating his 31st birthday, homered one out later to spark the host Philadelphia Phillies to a 5-3 win over the Arizona Diamondbacks.

Game 2 of the best-of-seven series is scheduled for Tuesday night in Philadelphia, where Aaron Nola is slated to start for the reigning NL champion Phillies against Merrill Kelly.

Schwarber, who entered Monday hitting .160 with no homers, one RBI and 10 strikeouts in 25 at-bats this postseason, sent the already enthusiastic crowd of 45,396 into a frenzy by hitting Zac Gallen's first pitch -- a 92 mph fastball -- 420 feet into the right field bleachers.

It was a record fourth career playoff leadoff homer for Schwarber.

"I don't know if anybody called it," Phillies right fielder Nick Castellanos, speaking to MLB Network following the game, said of Schwarber's homer. "But we've seen it so many times."

After Trea Turner lined out, Harper homered on the first pitch he saw from Gallen for his fourth homer of these playoffs and his 10th homer in the last two postseasons. He's the fourth player to go deep in a playoff game on his birthday, joining Willie Mays Aikens (1980), current Diamondbacks third baseman Evan Longoria (2013) and Kolten Wong (2015) in the select club.

"Hey man, he continuously shows out when he's supposed to," Castellanos told MLB Network. "He's locked in, man."

Harper is performing in the playoffs for the sixth time in his 12-year career, but Monday marked the first time he played on his birthday. The Washington Nationals were eliminated in the Division Series in 2012, 2014, 2016 and 2017 and the Phillies had an off day last Oct. 16, one day after they closed out a four-game win over the Atlanta Braves in the NLDS.

"I've always wanted to play on my birthday," Harper said in a pregame news conference. "I've always wanted to do this, so I'm excited to have the opportunity and the chance to do it."

Castellanos remained hot by homering in the third for the Phillies, who have 12 homers in their last three games -- the most homers in a three-game span in playoff history. Harper and Castellanos have eight of those round-trippers.

The Phillies extended their lead to 5-0 on RBI singles by Harper and J.T. Realmuto in the third and fifth innings, respectively, before the Diamondbacks began mounting a comeback against Zack Wheeler (2-0) and Seranthony Dominguez.

Longoria's leadoff single in the sixth snapped a streak of 15 consecutive batters retired by Wheeler before Geraldo Perdomo homered to right.

The Diamondbacks, who were 84-78 in the regular season and earned the final wild card before reaching the championship series for the first time since 2007, inched closer in the seventh. Christian Walker drew a leadoff walk and raced to third when Dominguez threw Gabriel Moreno's comebacker into center field. After Lourdes Gurriel Jr. lined out, Walker scored on Alek Thomas' sacrifice fly.

The Diamondbacks sent the tying run again to the plate in the eighth, when Jose Alvarado got Tommy Pham to line out to strand Ketel Marte at first, and in the ninth, when Craig Kimbrel closed out his third save of the playoffs by getting Gurriel to hit into a 5-4-3 double play.

"I just felt like we were going to weather the storm," Diamondbacks manager Torey Lovullo said. "We were going to find ourselves in this ballgame at some point. The deficit just became too large at five."

Wheeler gave up two runs on three hits and no walks while striking out eight over six innings. He has a 0.70 WHIP in nine career postseason starts, the lowest WHIP over any nine-start span for any pitcher in postseason history.

Gallen (2-1) allowed the five runs on eight hits and two walks while striking out four over five innings.

"It was just a big grind for him the whole day," Lovullo said.

--Field Level Media