PHILADELPHIA -- After cruising through the first two rounds this postseason, the D-backs hit a speed bump in the form of Zack Wheeler and the Phillies offense on Monday.

Wheeler overpowered the Arizona bats early with his fastball while the Phillies mashed three quick home runs off starter Zac Gallen to grab Game 1 of the National League Championship Series, 5-3, in front of a raucous sellout crowd at Citizens Bank Park.

It was the first taste of defeat for the D-backs this postseason as they swept the Brewers in the NL Wild Card Series and the Dodgers in the NL Division Series. In fact, against the Dodgers they never even trailed.

It was a different story Monday as Kyle Schwarber hit the first pitch of the bottom of the first inning for a home run. Two batters later, Bryce Harper homered. Then Nick Castellanos added one of his own in the second to put the Phillies up 3-0.

“I think they just ambushed him,” D-backs manager Torey Lovullo said. “I think they came out ready to jump on his fastball. There's no mystery that Zac fills up the zone. He has an aggressive fastball and aggressive mindset. They just counterpunched him.”

It was jarring to have their ace allow five runs in five innings, and the offense, which had been so potent against the Brewers and Dodgers, took awhile to regain its footing.

Part of that was certainly Wheeler being his usual nasty self, as he allowed a broken-bat single to Corbin Carroll to lead off the game but then did not allow another hit through five innings while the Phillies built a 5-0 lead.

“He's really good, credit to him,” D-backs first baseman Christian Walker said. “Seemed like he was throwing it where he wanted to. His stuff is always there, it's always plus, elite stuff. So when he's locating, it's tough to kind of settle in and feel like you get a good feel for executing the plan.”

The D-backs offense finally got going in the sixth when Geraldo Perdomo hit a two-run homer off Wheeler, and Arizona took advantage of some wildness and a throwing error by reliever Seranthony Domínguez to score another run in the seventh and cut the lead to 5-3.

They brought the tying run to the plate in both the eighth and ninth innings but couldn’t get it done against José Alvarado and Craig Kimbrel.

“That's one of the great qualities of this ballclub,” Lovullo said. “We compete. We compete all the time.”

While they didn’t come all the way back, they did show some fight, and they hope that will give them a little push heading into Tuesday’s Game 2, when they will be facing another elite pitcher in Aaron Nola.

“I think any time you can score runs, especially late, there's some momentum there,” Walker said. “That's a really good bullpen. There's a win there to put up a couple runs and generate some offense. It's a long series and I think trying to tax bullpen arms as much as we can, make guys throw in high-leverage, high-intensity moments, I think that benefits us in the long run.”

While the Phillies have Nola going in Game 2, the D-backs have an outstanding pitcher of their own going in right-hander Merrill Kelly. That, along with the late runs, had the D-backs feeling OK about themselves walking out of the ballpark.

“It can be a motivating thing to get punched in the face early on in the series and just be able to answer back and respond in a positive way,” veteran third baseman Evan Longoria said. “That’ll be the challenge tomorrow. Can we show up with the same kind of energy, the same kind of quality at-bats that we had early in the game and ultimately come through with some bigger hits?”

Gallen, who was disappointed in the location of the fastballs to Schwarber and Harper, knows his team has been underestimated plenty of times. They were the underdogs against the Brewers and Dodgers. They weren’t favored in this series with the Phillies either.

That hasn’t seemed to faze them.

“Sounds like you're counting this out after one,” Gallen said. “We’re going to show up.”