PHILADELPHIA -- A week ago, in the aftermath of their National League Division Series victory over the Dodgers, the Padres set about mapping out plans for Philadelphia. Pitching-wise, at least, the NLCS seemed fairly straightforward. With one caveat: Game 4 would be a challenge.

The Padres didn't know whether they could trust Mike Clevinger as their No. 4 starter. They didn't know whether Sean Manaea could cover the middle innings. They didn't know if they could avoid taxing their bullpen too heavily amid a potential stretch of five games in five days.

Baseball has a way of being brutally honest. The Padres had questions upon questions about their Game 4 pitching options. Sure enough, Game 4 came and went, and they got their answers.

The San Diego pitching staff was exposed in a nightmarish 10-6 loss to the Phillies at Citizens Bank Park, pushing the Padres’ season to the brink. They trail 3-1 in the NLCS and must now win three games in three days to stave off elimination.

“Anything can happen,” said right fielder Juan Soto, whose two-run homer in the fifth gave the Padres a lead before the wheels came off. “They have to win another game. We aren’t going to give them that win easy. We’re going to go out there and play our best, see what happens.”

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The task is daunting. In best-of-seven postseason series, 91 teams have fallen behind 3-1. Only 14 have rallied to win that series. If the Padres can’t become the 15th, they’ll be left with an offseason to rue some of the pitching -- and the pitching decisions -- in Game 4.

After half an inning, they had to have liked their chances. Manny Machado’s solo homer started a barrage of two-out hits, chasing Phillies starter Bailey Falter. San Diego led 4-0 before Clevinger even took the mound.

Then, Clevinger gave nearly all of that back. He faced four batters and did not record an out. Kyle Schwarber singled, Rhys Hoskins homered, J.T. Realmuto walked and Bryce Harper doubled him home. That early 4-0 lead was suddenly 4-3, and a once-stunned Citizens Bank Park had come to life. The Padres only managed to preserve their edge by calling for Nick Martinez far earlier than they anticipated.

“This was probably one of the worst days of my life,” Clevinger said. “That sums it up. It sucks.”

The Padres became just the third team to score four runs in the top of the first inning of a postseason game they ended up losing, joining Cleveland in the 1997 ALDS and the Washington Senators in the 1925 World Series.

Clevinger and Falter became the first pair of starters that couldn’t make it through the first inning of a postseason game since Game 4 of the 1932 World Series. Clevinger is just the sixth starter in postseason history to face at least four hitters without recording an out, and the first since Al Leiter in the 1999 NLCS.

“Look, just middle of the plate, and he didn't have his best stuff, obviously,” Padres manager Bob Melvin said. “I had to take him out pretty quickly. [Martinez] stabilized things. But [Clevinger] just couldn't get the ball where he wanted to. It ended up being a short night.”

Clevinger has battled knee trouble for much of the season, though he said he felt healthy on Saturday. He posted a 6.52 ERA over his final six starts of the regular season, then was roughed up for five runs at Dodger Stadium in the NLDS.

That the Padres turned to Clevinger to start such a crucial game speaks to one of two failings: They either got that decision woefully wrong. Or they constructed a roster without other viable options. Perhaps both.

And still, once Clevinger’s night was done, San Diego had a lead to protect. Martinez did so admirably, retiring all nine hitters he faced across the first three innings. But he threw 43 pitches -- his most since June. He hadn’t pitched three innings since July.

“You ask any competitor if he wants to go back out there, they’re going to say yes,” Martinez said. “I felt good. But with the guys we’ve got in the bullpen, I have a lot of confidence in those guys and so does Bob.”

Clevinger’s early exit meant that at some point, Melvin was going to need outs from his lower-leverage relievers. He turned to Manaea, who hadn’t pitched since Oct. 4. Manaea surrendered the tying run in the fourth, but things didn’t spiral until the fifth.

The inning began with two lefties for the lefty Manaea -- and Melvin liked those matchups. Manaea struck out leadoff man Brandon Marsh. But he walked Schwarber, putting the Padres in a precarious position for the Phillies’ 2-3-4 of Hoskins-Realmuto-Harper.

Right-hander Luis García was getting loose but wasn’t quite ready for the righty-hitting Hoskins. Melvin stuck with Manaea, and later explained his decision thusly:

“We were trying to get him through Harper. That's kind of where we're at. He strikes out Marsh, looked good, had good velo on it. He walked Schwarber on some close pitches, and at that point in time we're trying to get him through Harper.”

And that’s where the game swung. Hoskins responded to Soto’s home run with a two-run homer of his own. By then, García was ready, but Melvin feared a matchup between García and the lefty-hitting Harper. (García, who later allowed a home run to Schwarber, struggles with lefties.)

So Manaea remained in the game and walked Realmuto. Harper doubled him home. By the time Melvin emerged -- perhaps a batter too late, perhaps four batters too late, but too late nonetheless -- the Phillies had a lead they wouldn’t relinquish.