Kozak, 26, joined Villa in the summer of 2013 having hit 22 goals in 80 games for Italian side Lazio, but his time in England hasn't been a happy one.
The Czech striker has struggled with injury problems throughout his time at Villa, playing just 15 games with only four goals to his name.
This term, Kozak has been on the fringes of the Villa side once again despite being fit, and he played for the club's Under-21 side against Derby County on Monday night.
Kozak proved what he can do in front of goal by scoring both goals in Villa's 2-1 victory, and it seems that one manager was watching his performance.
The Scottish Sun report that Celtic boss Ronny Deila travelled down to watch Kozak in action ahead of a possible January move for the giant forward - even after signing Carlton Cole on a free transfer.
It's stated that Celtic tried to sign Kozak over the summer, but he rejected the move to Celtic Park. Yet, with his first-team prospects no better at Villa, he may well reconsider a deal with the Bhoys in January - unless new Villa boss Remi Garde does decide to give him a chance in the first team in the near future.