From the moment word emerged that 11 Philadelphia Union players would miss Sunday's Eastern Conference final due to MLS health and safety protocols, attention was rightly focused on the five starters who would sit out.

The likes of goalkeeper Andre Blake and captain Alejandro Bedoya would be spectators. So would three fourths of the usual backline, with center-backs Jack Elliott and Jakob Glesnes as well as left-back Kai Wagner also out. But the knock-on effect was that the Union would have precious little depth to change the course of the match should that be required. Opponents New York City FC were missing some key players as well, most notably MLS Golden Boot winner Valentin Castellanos, but it was obvious that manager Ronny Deila had more resources on his bench than counterpart Jim Curtin.

In the end, that proved to be the difference, as New York City came from behind to win 2-1 thanks to substitute Talles Magno's late goal, and set up an MLS Cup showdown on Saturday with the Portland Timbers (3 p.m. ET, stream live on ABC).

Conference finals are rarely remembered, save by the fans of the teams who win them, even if there is a contrived trophy presentation at the end. MLS Cups make more of an impression. But such was the gutty performance by the Union -- as well as NYCFC's comeback -- that Sunday's encounter will likely stick in the memory a bit longer than most.

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The circumstances alone made for a unique matchup. Word emerged Friday that the Union were hurting in terms of personnel. On Saturday, there was confirmation that 11 players would be out, and there was concern that the game might devolve into a farce unbecoming of a conference final. For Curtin, even filling out his lineup card was a challenge.

"When I was writing in the team messages at the beginning of the game there are a couple of names I didn't know how to spell quite yet, so I had to do some peeking at the backs of jerseys, which is a situation that was unique for sure," he said.

Fortunately, that blowout scenario was avoided. While Deila was complimentary of the Union players who took the field, and noted that Philadelphia's style didn't change, he admitted that the home side's depleted numbers did change the mental dynamic of the match.

"It has a different pressure to us to be more, 'We have to win,' instead of, 'Amazing to win,'" he said.

Perhaps that explains the rather tepid nature of the first half, when NYCFC had the vast majority of the ball but never really threatened the Union goal. In fact, Philadelphia's patchwork backline led by Aurelien Collin -- who had played one minute of competitive soccer for Philadelphia the past two seasons -- looked comfortable for the better part of an hour. And when Kacper Przybylko forced an own goal from Alex Callens in the 63rd minute, it really looked like the Union would get their "Rocky" moment.

But after scaling the mountain, the Union's legs weren't strong enough to stay there. The lead lasted all of 110 seconds, with Maxi Moralez hammering home a rebound to bring NYCFC level. From there, the Blues were running downhill.

"I think we needed to get a period to get the crowd into it, to have a five-minute window where now it puts a little stress and pressure on New York City," said Curtin. "Maybe they start to throw numbers forward and we can hit them on the counter."

By then, Deila had already made a trio of substitutions, turning to record signing Magno, Gudmundur Thorarinsson and Ismael Tajouri-Shradi, all of whom helped tip the balance toward the visitors. Thorarinsson got forward with greater effect than Malte Amundsen, while Tajouri-Shradi and Magno perked up the Blues' attack in the final third.

As for Curtin, he was hamstrung, with little in the way of options as his valiant band of starters was gassed.

"They had some weapons that came off the bench that I'll just say are expensive," said Curtin.

The most expensive one of all delivered with less than two minutes of normal time remaining. Thorarinsson robbed Olivier Mbaizo, and fed Magno -- a $12 million midseason acquisition -- to fire home the game-winner from close range in the 88th minute.

The goal was cruel on the Union, especially given that Nathan Harriel sent a free header over the bar just minutes earlier. But it seemed deserved for an NYCFC side that slowly turned up the pressure after halftime.

"I think we were the dominant team in the second half," said Deila. "And we knew that in the last minutes of the game, we will get more space and [create] more chances, and we did. The substitutes worked really, really good. You saw how fresh they were."

Curtin is the kind of manager who isn't one to give into excuses, but he couldn't help but let his mind drift into what-if scenarios. Nine months of sweat and effort went down the drain due to a virus that remains stubbornly part of American life. Without going into specifics, and stressing how he's a firm believer in science, Curtin felt that the league's COVID-19 protocols could do with some tweaking given "we had 11 guys that are healthy to play a soccer game that aren't here because they have a version of sniffles."

He added, "You're at a loss for words, man. I just feel bad for the guys that weren't here, because again, they had incredible seasons. COVID sucks. I don't know how else to put it. The protocols are the protocols, but could they be updated, adjusted for common sense? I don't know. Again, it hurts."

That pain will linger for a while in Philadelphia. Meanwhile, it is NYCFC who will move on to MLS Cup.

"What we have done so far, it's been just amazing," Deila said. "But the biggest one is coming on Saturday."