The Socceroos star is set to feature in the opening game of the season when Huddersfield travel to face Crystal Palace on Sunday (AEST).
Mooy enjoyed a hugely successful season-long loan last term in the Championship as the unfashionable Yorkshire outfit reached the top flight for the first time since 1972.
The 26-year-old subsequently made a permanent A$17 million move from parent club Manchester City despite being linked with the likes of Palace and Newcastle United.
Mooy joined City from sister club, and A-League outfit, Melbourne City in June 2016 but did not make an appearance for Pep Guardiola’s side.
Having made his name at Huddersfield, manager Wagner has no doubts about his star midfielder’s ability to cut it against the likes of Liverpool, Chelsea, Arsenal, Manchester United and his old club City.
Wagner denied that Mooy would be under scrutiny this season because of his hefty price tag.
"Compared to the players in the Premier League, and the money that has been spent on them, I think there should be no pressure on Aaron," Wagner said.
"Like him, we all have to prove that we are Premier League players and a Premier League club as well.
"We have all showed that we are a very good Championship club with very good Championship players.
"Aaron as well has to prove himself at the next level and I’m totally sure he will do it."
Wagner granted Mooy a late start to the pre-season after his Socceroos commitments in June at the 2017 FIFA Confederations Cup capped off a gruelling 61-game season.
Mooy has caught up on his fitness despite his shorter pre-season, after an arduous training camp in the Austrian alps.
"Aaron and maybe Tommy Smith and Michael Hefele came into pre-season late so therefore they need some more time to reach the level of other players, who have had a full pre-season," Wagner said.
"But this is something that always happens in pre-season, yet my expectation is that Aaron will be able to give our team the same contribution as he did last season.
"This is why we signed him on a permanent basis and I have no doubt he will prove himself at this level in the Premier League."