As the Manchester United players departed the field after a training session, the Barcelona players walked onto the pitch at Washington DC's Fed Ex stadium in late July.
Some of the rivals let on to each other, the bigger names who'd lined up against each other at Wembley only two months previous. Many of the players didn't recognise their foes, such was the number of reserve players in both squads. No Barca players recognised Tom Cleverley and for sure no United players knew Isaac Cuenca.
Cuenca might have pinched himself to check he wasn't dreaming. A year earlier, Barcelona's B team boss and current AS Roma coach Luis Enrique looked through the prospects available and completely bypassed the callow winger from Reus in the south of Catalonia.
The youngster who was famous in his barrio for walking to school while playing keepy-uppy with a football.
Cuenca, then 18, was sent on loan to third division Sabadell. Just as Cleverley had prospered from his loan moves to Leicester, Watford and Wigan, so Cuenca thrived at Sabadell, the team from a working class city of 200,000, 20 kilometres from Barcelona. His new team were promoted to Spain's second division for the first time in 18 years and Cuenca played a starring role.
"It was a great experience for me," Cuenca told me after Tuesday's Champions League game. "I played every week and felt myself improving as we won the league. It was a very happy year in my life."
Such was his affinity with Sabadell, he stayed living there with a local girl, but for his day job he returned to Barca. He was immediately called up to Barca's first team squad for the pre-season tour. It seemed Pep Guardiola had seen something in this graduate of the Masia which Luis Enrique had missed. Cuenca didn't travel just to be a passenger and found himself playing in Washington against United in front of a huge 81,807 crowd.
"After the tour, I expected to go back to Barca B and win a place in that team," says Cuenca.
"I knew that would be difficult though, so maybe my aim was to play as many minutes as possible for Barca B."
He did drop back into the Barça's B team in Spain's second division, a player with a squad number of 39 wouldn't have expected anything else and besides, it was still a step up for him as he'd never played in that division.
He'd have another surprise a few months into the season. With winger Ibrahim Afellay injured, Cuenca was called up as a sub for the first team for Champions League game against Viktoria Plzen.
"When the coach told me to go on the pitch, well, that was the highlight of my life so far," he says. "It was only a couple of minutes at the end, but there I was playing in a real game in Camp Nou. For a Barca B player that was a dream. For a Barca fan it was a dream. I've always supported the club and so have my family. My idols were Rivaldo when I was really young and then Ronaldinho."
A week after his three minute Champions League cameo, Cuenca made his first start in a league game at Granada.
"That went well too and I found myself learning every day in training from the first team players," he says. "They were great with me and the mister (Guardiola) always has small pieces of advice for me."
Cuenca has since started five times for Barça and scored his first goal on Saturday.
"He has good movement, confidence and knows role in team," says former Barca striker Steve Archibald. "Young players don't often take their chance but Cuenca has. He gets a lot of the ball which shows that his team mates have confidence in him. That will help him no end."
Cuenca stretches Barca wide by hugging the line, he crosses well and cuts inside to assist.
Lionel Messi set him up for his first Barca goal in Saturday's 5-0 victory over Levante, with a pass across the edge of the area which Cuenca guided home. There was praise for him after the game too from his manager, though it might not have been quite what he was expecting.
"Maybe the girls don't like him," said a smiling Guardiola in the press conference after the game, "but he plays perfectly." Cuenca merely blushed and replied classily, "You'll have to ask the girls."
It was an unfair comment, but Guardiola adores the young winger, and if a Barca player is going to have a biggest fan who better than Guardiola?
Cuenca has also been called up for Spain's U21s, the current European champions, alongside David de Gea, Oriol Romeu, Iker Muniain and Thiago.
And he started last night as a weakened Barca team beat BATE Borisov 4-0. Cuenca enjoyed his best performance to date, a man of the match in which he set up the second and third goals in a manner of which Iniesta or Xavi would have been proud.
Will he play in Saturday's key Clasico against Real Madrid in the Bernabéu?
"That's up to the coach," he says, "but I'm ready if I am chosen. I will do nothing differently. My feet are on the ground, whether I'm chosen for the first team or the B team."