Huddersfield take on Sheffield Wednesday on Sunday in the Championship playoffs with a potential place in the English Premier League on the line.

Mooy has been a revelation for the Terriers since his arrival from Melbourne City. The midfielder has made 48 appearances, scoring four goals and setting up 10.

“Aaron has been top class,” Wagner said.

“Usually when he plays well, the team plays well – Aaron is the heart of our team. He knows exactly when to accelerate or decelerate the game and when he’s under-performed, we’ve often had problems too.

“When you consider how much he’s been involved with the Australian national team, with all the travelling and time differences and things like that, it’s been a very tough season for him but he’s still able to deliver his best.

“Stuart Webber mentioned Aaron to me at the end of last season, then he showed me some clips and I watched England v Australia at Wembley and decided to loan him. Man City were interested and we were able to sign him.

“There’s communication between me and Man City, not just about Aaron but other potential players. After we showed we can develop a Man City player, they’re interested in working with us in future.

“They had a callback clause on Aaron they could’ve used in January but they saw he was on the right path. Then when we played them in the FA Cup, I had chance to speak about him with Pep Guardiola.”

If Huddersfield get past Wednesday then Reading or Fulham will await at Wembley for a spot in the Premier League. The Terriers last played in the first-division 45 years ago.

Wagner believes getting his club promoted to the top flight would rank just as high as Leicester City winning the Premier League last season.

“If we get promoted, this is for sure a reload of the Leicester story,” he said.

“I didn’t use Leicester as an inspiration where I say to my players, ‘Look, they’ve done it. We will do it as well. But if it happens, this will be a similar surprise or achievement for this club like it was for Leicester.

“To be honest, I didn’t expect us to be in this position at the start of the season. I knew during pre-season that we wouldn’t be involved in relegation trouble, even though some experts predicted we’d get relegated.

“Then after the first 23 games, around Christmas time, I was pretty sure that we had a realistic chance. I’d always said it was unrealistic but then around Christmas, I thought, ‘OK, it’s realistic now.’

"I never thought we’d get automatically promoted, though – Brighton and Newcastle are so strong. It’s too far away to think about the Premier League, even though it’s only three games away.

"I’d be wasting my energy thinking about whether we’d be competitive in the Premier League.”