Aston Villa boss Unai Emery thought Emiliano Martinez had been sent off in a chaotic penalty shootout against Lille before the goalkeeper made the save that sent his side through to their first major European semi-final since 1982.
In an extraordinary shootout after the tie ended 3-3 on aggregate after extra time, Villa keeper Martinez - who had been booked earlier for time-wasting - was shown another yellow card for appearing to gesture to home fans.
Martinez, who had already kept out Nabil Bentaleb's penalty, was allowed to carry on as his initial booking was not carried over into the shootout.
The Argentina World Cup winner then went on to keep out Benjamin Andre's attempt as Villa won 4-3 on penalties to advance to the last four.
Martinez then ran virtually the whole length of the pitch to celebrate in front of Villa's jubilant 2,600 travelling fans.
Asked whether he and his players thought Martinez had been dismissed in the shootout, Emery said: "Yes. He is very important for us.
"On the pitch he has his personality and he played fantastic. He saved two penalty shots so of course I am very proud of him."
Earlier in the shootout, Ollie Watkins was made to wait to take his penalty as there were two balls on the pitch before the England forward stepped up to score.
On a dramatic night in northern France, Emery's side were three minutes from going out after goals by Yusuf Yazici and Benjamin Andre wiped out Villa's 2-1 advantage from the first leg.
But Matty Cash's 87th-minute deflected strike - after goalkeeper Lucas Chevalier had dropped a cross - made it 3-3 on aggregate and forced extra time which did not produce any further goals leaving the tie to be decided by penalties.
Aston Villa will face Olympiakos in the semi-final after they defeated Fenerbahce on penalties later on Thursday.
Martinez had been jeered throughout the game by Lille fans after his penalty heroics in Argentina's World Cup final victory over France in 2022.
He was shown his first yellow card of the game in the first half for time-wasting, and there was confusion inside the ground when the Villa keeper was allowed to carry on after being booked again during the shootout - as the rules state yellow cards are not carried over into penalties.
"Yesterday you [the media] were all asking me about the reception he [Martinez] will get here in France and you could see it throughout the game," added Emery.
"He is very experienced and he was trying to control his emotions but the supporters were pushing him. I believe in him and he is mature but with personality. He is always under his own control."
Martinez defended his actions after the game.
"It's all about reputation for time-wasting because the other goalie was doing exactly the same thing," he told TNT Sports.
"I got a yellow after 30 minutes and we were losing the game so I don't know what the ref wants from me.
"Then there was no ball in the penalty spot and I was asking for a ball from the ball boy and I get booked; I just don't understand the rules.
"I am a believer and a hard worker and it was my destiny today."
It all added to the drama as Villa dug deep to ensure one English club will compete in a European semi-final this season after Manchester City and Arsenal were knocked out of the Champions League on Wednesday, and Liverpool and West Ham exited the Europa League on Thursday.
This was not Villa's finest display by any stretch of the imagination but they managed to stay in the tie when 2-0 down before Cash provided a late lifeline.
The Europa Conference League might be Uefa's third-tier competition but Villa are enjoying the ride.
By staying in it, they remain on course for a top-four finish in the Premier League and a first major European trophy for 42 years in Emery's first full season in charge.