The Czech striker has been linked with a move to Parkhead since the start of the season.
Kozak made his first appearance of Garde’s reign last weekend when he replaced the injured Alan Hutton for the final 15 minutes of Villa’s 3-1 defeat at relegation rivals Sunderland.
It was the 26-year-old Czech’s first Premier League run-out since breaking his leg in training in January 2014, having spent the following 19 months out of first-team action after needing a second operation following a setback in his rehabilitation.
His long-awaited return to the senior set-up this past preseason saw him bag three goals in five friendlies, suggesting that a successful comeback campaign was in store, but the fit-again front man instead made just one substitute appearance in the Capital One Cup over the first half of the term.
Villa fans have been crying out for him to be handed more playing time after seeing the club score a division-low 16 goals in 20 league games, but Garde has continued to maintain that the former Lazio forward is no better than his other attacking options.
The ex-Lyon boss revealed last month that Kozak would be free to leave in the January transfer window if an offer came in for his signature, and despite bringing him back into the first-team fold for the Sunderland game, he does not appear to have changed his tune since.
Speaking about the little-used striker’s Villa future, Garde told the Birmingham Mail: “Libor has been asked about. I had a phone call yesterday night, but I don’t know yet. He could be [moving].
“He has been linked in the past I have been told with a few clubs and not left this football club, so I don’t know exactly.
“I answer fairly to your question but I haven’t spoken yet to Libor about the phone call - then I can say more.”
While the identity of the club making the enquiry remains a mystery for now, it would certainly be no surprise if the suitors in question were Celtic given their long-running interest in Kozak.
The forward reportedly rejected a switch to Parkhead in the summer, but Bhoys boss Ronny Deila has since watched him in action for Villa’s Under-21s and is now said to be preparing another move for his services [h/t Daily Record].
Garde himself has even acknowledged the Scottish champions’ interest in the eight-time capped Czech Republic international last week, telling the Birmingham Mail: “I have heard about this information and the link between Celtic and Libor, but then it's more down to him."