A film about Sir Elton John's life is being released the day before Watford play in the FA Cup in May.

The script for Rocketman has already been written but if Gerard Deulofeu can produce more Wembley heroics against Manchester City then the director may need to add an extra scene.

John, the former Watford owner and now the club’s life president, was in tears at the final whistle on Sunday after Deulofeu inspired their comeback against Wolves. The singer is expected to be at Wembley next month and, 35 years after watching them lose to Everton in their last FA Cup Final, seeing his beloved club lift their first major trophy would be a lifetime highlight.

Deulofeu was the Watford hero at Wembley, sparking one of the great comebacks to send them to their only their second FA Cup Final and their first since 1984.

The label of the “next Messi” weighed heavily on Deulofeu but the mercurial winger is finally beginning to fulfil his potential under Javi Gracia. In 46 inspirational minutes, he showed why he was once regarded so highly. Brought on as a 66th-minute substitute with Watford trailing 2-0, he sparked their revival with a sublime chip 11 minutes from time. It was a moment of magic and, after a last-gasp penalty from Troy Deeney took the game to extra-time, the Spaniard scored the winner.

Deulofeu struggled for consistency at Barcelona, Everton, Sevilla and AC Milan but he is now playing some of the best football of his career under Javi Gracia. Once considered as the heir to Messi at Barcelona, he is still only 25 and his cameo showed why he feels he can get back to playing at a top club in Europe. Deulofeu had been furious when he found out he was not starting. An ineffective display against Fulham last week meant Garcia started Andre Gray ahead of him. But that anger helped inspire Watford to seal a place in the final against City.

“He [Gracia] knows I am angry,” said Deulofeu. “Because I have been playing all season. But sometimes the manager has to make decisions. I did what I had to do. When I was younger, I scored some goals like this at Barcelona.

“I saw the keeper up a bit and I put it over into the corner. Then with the penalty, Troy has so much experience. My thought was we could go on and win it.”

One of Deulofeu’s biggest regrets is that he never had the chance to develop under Pep Guardiola. He was handed his Barcelona debut by Guardiola in October 2011 but made just two appearances during the manager’s final season.

Deulofeu struggled to win the trust of a succession of managers during loan spells at Everton and Sevilla, then a permanent move to Goodison Park and a loan to Milan before a brief return to Barcelona. But since joining Watford for £11.5million last summer he has flourished under Gracia and now wants to stop Guardiola winning the quadruple.

Watford will be underdogs against City on May 18 but the character they showed to fight back against Wolves, plus the quality provided by players like Deulofeu, means they should not be written off. The Hornets hope the Premier League title run-in and their Champions League quarter-final with Tottenham will take something out of City.

But, for now, Watford will enjoy their moment. Deeney said: “We will worry about City the week before. This is not their moment, this is our moment. This is for everyone who has been with us on the journey, who were here when the club was close to administration.

“We should bask in it because we deserve it. This team has got something special. We are not the most talented, but we work hard. At 2-0 down many teams would have called it a day but we kept going, brought the little man on who added a bit of magic and then the rest is hard work.”

Nobody at Watford deserves an FA Cup Final at Wembley more than Deeney. He showed the “cojones” he once accused Arsenal of lacking to score a 94th-minute penalty which forced extra time.

An emotional Deeney reflected on a journey that has taken him from non-League football and prison to a chance to make history with Watford.

“For the first time ever I looked at it from a selfish point of view,” he said. “I had a toast with my family after the game. I have come a long way. People always go back to when I was in jail but before that, just grafting away and trying to be a footballer.

“It has been a long, hard stint to get here and that was the emotion at the end. I am not going to lie I was holding back the tears. Twelve years I ago I was paying £10 a week to play football. Now I am going to be in the FA Cup Final.

“Every now and then you have that moment where it is a wave of emotion that hits you. I had a moment with my mum which was special. This moment means everything to me.”