The Australian midfielder, who has been one of the Terriers' key men since his arrival in 2016, has been tipped for a last-minute move to Brighton and Hove Albion.
The transfer window closes at 5pm today (Thursday) leaving the Premier League outfit with just a few hours to get a potential deal over the line.
However, Premier League clubs are allowed an extra two hours to complete a transfer if they submit a deal sheet before the 5pm deadline.
A deal sheet allows the Premier League to see that a deal has been agreed, giving clubs until 7pm to submit all the relevant paperwork.
Mooy featured for Huddersfield in their 2-1 defeat to Derby County on Monday night in what could have been his last game for the club.
"We have been honest from the first day and we knew it would always be a difficult transfer window," said Siewert.
"For players like Aaron Mooy, who have played in the Premier League and proved their quality in the Premier League we knew there might be some offers."
Siewert added: "Nothing is agreed. For me it is important that we have talented players here and Aaron is a talented player."
The Town boss remained tight-lipped on any potential incomings for Huddersfield, who have already lost Philip Billing to Bournemouth.
"I never speak about other players who are not in my squad because I think it is disrespectful," added Siewert.
"I just think about my squad at the moment and I am focusing on QPR."
Meanwhile, Seagulls boss Graham Potter is hopeful that Brighton can complete a deal before the deadline.
"There's nothing to report yet in terms of finalising it but I think we're quite close. We’re going to try and get it done but until then he's not our player," said Potter.
"I think he's had really good experience recently in terms of that he's got experience in a promotion winning team and he's got experience in the Premier League.
"He’s had some disappointments as well and I think that’s part of football and how he uses that experience overall to help us."