The Terriers' German coach turned down the chance to take over at Wolfsburg earlier this year, and is now being linked with a possible return to Borussia Dortmund, where he once assisted close friend Jurgen Klopp, or Bayer Leverkusen next season.

Such is the impression that Mooy has made on Wagner during his decorated loan spell from Manchester City this season that it's anticipated he could seek to sign Mooy from his parent club, whether he goes or stays.

Huddersfield must beat Reading in next Tuesday's Championship final to clinch at spot in the Premier League.

But there is no guarantee that a wanted Wagner will stay at the John Smith's Stadium, even if they are promoted.

Those fears have been heightened amid rumors that owner Dean Hoyle is looking to sell the club and is reluctant to provide the necessary funds to significantly bolster the squad.

Wagner has personally reconfigured Mooy's game, transforming him from a playmaker to a number 8, and cajoling the sort of form for him which has already generated offers from Newcastle United and Crystal Palace and brought him Player of the Year recognition Huddersfield and a spot in the EFL Championship's Team of the Season.

Wagner showed his appreciation of the flowering of project Mooy when he said earlier this month: "Aaron has been top class, usually when he plays well the team plays well. He is the heart of our team.

"He knows exactly when to accelerate and when to decelerate the game, and when he's under performed we have often had problems too."

Despite Mooy's influence this season, Wagner has made it clear he feels "there is another gear" in the 26 year old, who should the planets align could join fellow Socceroos Mitch Langerak and Mathew Leckie in the Bundesliga.

Wagner has been mentioned with the future of Dortmund coach Thomas Tuchel in question after a fallout with CEO Hans-Joachim Watzke, despite the fact they have qualified for the Champions League and are in the final of the DFB Pokal.

There is a vacancy at Leverkusen - Socceroo Robbie Kruse's former club - following the recent sacking of Roger Schmidt.