PHILADELPHIA -- The National League Division Series schedule set up perfectly for the D-backs when it came to starting pitching.

With off-days between Games 1 and 2 and another between Games 2 and 3, the D-backs knew they’d need just three starting pitchers. And had the series gone the full five games, they could have started their two aces -- Zac Gallen and Merrill Kelly -- in four of them.

After sweeping the Dodgers, the D-backs have Gallen and Kelly lined up to pitch against the Phillies in Games 1 and 2 of the NL Championship Series.

But with off-days now only after Games 2 and 5, the D-backs are going to have to use two other starting pitchers -- and that’s where things get a little tricky for them.

“We're going to get into longer series now, and we'll see how that goes,” said D-backs general manager Mike Hazen.

One encouraging sign for the D-backs was the performance of rookie right-hander Brandon Pfaadt in Game 3 against the Dodgers.

Pfaadt allowed two hits over 4 1/3 innings, and at just 42 pitches he could have gone deeper into the game, but manager Torey Lovullo has been aggressive in going to his bullpen this month. He’s said that while Gallen and Kelly get a slightly longer leash, the other starters on his staff would get to face 18 batters, give or take four or five.

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Pfaadt, who struggled in his first couple of stints in the big leagues this year before pitching better down the stretch, figures to get the ball in Game 3, though the D-backs are officially TBA beyond Kelly in Game 2.

“I think the way Torey has managed the bullpen and the pitching staff has been incredible,” Hazen said. “I think our bullpen is deeper than it's ever been, and that's going to serve us well. Zac and Merrill hopefully getting at least two starts in the next round will at least put us on a path, and then the way Brandon threw [in Game 3] was unbelievable. If we get that from him, we’ll be a dangerous team.”

Assuming they use Pfaadt to start Game 3, that leaves Game 4 still to be filled.

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Lovullo sat down with his coaching staff and baseball operations personnel to discuss the starting pitching prior to Friday’s afternoon workout at Chase Field. They laid out all kinds of different scenarios, from Gallen and Kelly pitching deep into Games 1 and 2 to a short start by one of them that would require the assistance of a number of bullpen arms.

“We have to prepare for the best-case and worst-case scenarios,” Lovullo said. “So we hit just about every scenario that we possibly could.”

One thing that seems certain is that the D-backs will alter the composition of their roster from the NLDS to the NLCS. Instead of utilizing 14 position players and 12 pitchers as they did against the Dodgers, they will likely go with an even split against the Phillies.

Ryne Nelson is the most likely candidate if the D-backs go with a traditional starter for Game 4. The rookie right-hander appeared in 29 games for Arizona this year, 27 as a starter, and was 8-8 with a 5.31 ERA.

It’s also possible that the D-backs opt for an opener in Game 4. It’s a concept that the club had mostly rejected the last several seasons, but one it began embracing this year after the losses of starting pitchers Zach Davies, Tommy Henry and Drey Jameson to injury.

Left-handed reliever Joe Mantiply started three games as an opener for the D-backs, and if the Phillies have a couple of lefties hitting in the top five spots of their order, they could use Mantiply for the first inning-plus before turning the game over to Nelson or fellow rookie Bryce Jarvis, with their traditional bullpen arms waiting in the wings to match up in the mid-to-late innings.

Of course, having Gallen and Kelly pitch relatively deep into the first two games of the series would be ideal, and would help save some innings that will be needed from the bullpen in Games 3 and 4.

For now, count on Gallen and Kelly in the first two games and likely Pfaadt in Game 3.

After that … stay tuned.