When the whistle sounded to end the second extra time period Sunday night at Subaru Park, not all was well on the Union bench.

There was plenty of reason to have faith in goalkeeper Andre Blake, of course. But when it came to who would take penalties for the Union, it wasn’t so simple.

The Union don’t really have a designated penalty kick taker for most games. In the last three years, Kacper Przybylko, Dániel Gazdag, and Jamiro Monteiro have all stepped to the spot at various times, with Przybylko taking (and scoring) two of the three penalties the Union were awarded during this year’s regular season.

This time, Przybylko and Monteiro were unavailable because they had been subbed out. So who would step up?

“It wasn’t straightforward, the five that were selected,” Union manager Jim Curtin said after the game. “Some guys were feeling good, some guys weren’t at the moment.”

» READ MORE: Andre Blake leads Union to MLS Eastern Conference final with penalty kick shootout heroics

It wasn’t surprising that after Blake stopped Nashville star Hany Mukhtar to start the shootout, Jack Elliott stepped up for the Union. He’s the most levelheaded player on the team, and there’s nothing you need more in a moment like that. Elliott duly scored with an easy low finish. Then Blake stopped Aníbal Godoy with a terrific full-stretch dive.

And then Subaru Park was really stunned.

Was that really 18-year-old rookie Jack McGlynn, the player who had subbed in for Monteiro, walking to the spot?

Yes, it was.

The Union academy product from Queens, N.Y. — who had, by the way, been passed over by New York City FC and the Red Bulls growing up — showed throughout this year that he has great composure on the ball. He’s also got a high motor and makes plenty of defensive contributions in central midfield.

But this was different from anything else he had done to date in 655 minutes on the field over 24 games, usually as a close-it-out substitute.

Or so everyone else at Subaru Park thought.

» READ MORE: Jack McGlynn showed great potential in his first pro start back in May

McGlynn didn’t just score comfortably. He hit Nashville goalkeeper Joe Willis with a stutter step in his run-up worthy of a veteran star from Brazil or Argentina. Willis bit, then watched McGlynn curl a low shot, sending the ball toward Willis’ right side as he dove to his left.

To top it all off, McGlynn pointed to the vein in his right arm as if to indicate there was ice in it.

“How about that for coolness?” ESPN play-by-play announcer Adrian Healey said up in the broadcast booth. “Jack McGlynn without a care in the world.”

Standing next to Healey was one of the Union’s original players, Alejandro Moreno. Having been informed by Healey before the kick that McGlynn had family roots in Scranton, Moreno mused: “Scranton, you say, huh? Even Dunder Mifflin is proud of this. Let me tell you something — that is class right there from Jack McGlynn.”

In fact, McGlynn isn’t the first person to put Scranton in the spotlight while wearing Union colors. That honor goes to the team’s most famous fan, President Joe Biden, who has followed the team ever since he stood on the field at the Linc with the late Walter Bahr at the Union’s inaugural home game.

Biden might also appreciate the, shall we say, forthrightness of Curtin’s postgame praise for McGlynn.

“When a young kid says ‘I want one,’ you reward him with it,” Curtin said. “And again, for him to step up in that moment, there’s a word for it that I won’t use on the press conference — but he has brass ones. He’s stepped up in a big spot, in a full stadium, in an elimination game, and calmly just goes about it like it’s nothing.”

The players were just as impressed — but not surprised.

“These young players are really good,” said Gazdag, “I can speak about Jack McGlynn or also the others. I was sure that he would score his penalty.”

(Gazdag, by the way, was to be the fifth shooter, and Kai Wagner was to be the fourth. Both proved unnecessary when Nashville went 0-for-4, ending the five-round shootout in the top of the fourth frame.)

Blake was sure of it too, from all that he has seen of McGlynn in training this year.

“He’s a great player. He’s humble. He listens, and he wants to learn, [and] he’s very technical,” he said. “We had no doubt in him. He shoots every time in training, so we know how well he hits the ball. We know that he’s confident, so we had no doubt putting him in the top five and he went out there and executed.”

» READ MORE: Andre Blake writes another chapter in his Union legend with playoff penalty shootout heroics

» Join The Inquirer’s soccer staff for live coverage of the Union’s Eastern Conference final showdown with New York City FC on Sunday in Union Gameday Central. Kickoff is set for just after 3 p.m.