The 27-year-old has featured in every match for Huddersfield this season, scoring four goals along the way and emerging as one of the Terriers’ most influential players.
In a week when Liverpool paid an astonishing £75 million (A$129 million) for Southampton defender Virgil van Dijk, the £10 million (A$17 million) Huddersfield shelled out for Mooy in June increasingly looks money well spent.
The Socceroo’s impressive performances have attracted admiring glances from a number of higher-placed clubs and the transfer window will open on January 1.
Yet Wagner won’t be cashing in on the Sydneysider.
“Other clubs can save their money because we will not sell any player in this window who I don’t want to sell,” he said.
“Aaron Mooy, for sure, is one of those players because he was the stand-out midfielder in the Championship last season.
“He’s been outstanding in the Premier League as well, so it doesn’t surprise me that people are aware of him.”
Mooy has had a relentless run of games in 2017 for both club and country.
The Australian was the driving force behind Huddersfield’s fairytale promotion last season, as the Yorkshire outfit returned to English football’s top flight for the first time since 1972.
His displays during a season-long loan earned him a permanent move to the Terriers in a club-record transfer from Manchester City at the end of the campaign.
During the calendar year, Mooy played 10 times for Australia, including the vital World Cup qualifying playoffs against Syria and Honduras, as the Socceroos booked their place at Russia next June.
He has also amassed 48 matches for his west Yorkshire club in all competitions, meaning he has managed a total of 58 appearances in the past 12 months.
Dismissing fears of burnout for the former Western Sydney Wanderers and Melbourne City star, Wagner said: “I haven’t made my mind up finally whether to give Aaron a rest, but there are always players who play more minutes than others.
“This is part of the game and we will see how Aaron looks and then make a decision, but he’s a hugely important player for us.
“I’m not surprised by how well he has done in the Premier League and I expected him to be very good again at the higher level.
“He was the stand-out midfielder in the Championship last season, he dictated the game, and this is what I expected from him in the Premier League as well.
“He is the man in our midfield who is able to dictate the game, accelerate when necessary, and decelerate when necessary.
“He has adapted to every level he’s had in front of him and this is exactly what he’s done again this season.
“Usually when Aaron Mooy plays well in the midfield, we perform as a team and he’s a very important player for us, for sure.”