Reading are also interested in Martyn Waghorn.
Both Sheffield Wednesday and Reading are keen on the forward, who has already scored 25 goals this season.
Waghorn netted a hat-trick at the weekend, and told the Daily Record he is confident he can surpass 40 goals.
It is not surprising the form of the former England under-21 international is attracting interest, but manager Mark Warburton will do his utmost to keep his star man.
Waghorn, 25, only signed for Rangers in the summer from Wigan Athletic, and has previously been at Sunderland and Leicester City. In addition to this, he has been on loan spells with Hull, Charlton, and Millwall, but this is the best spell of his career so far.
Clearly enjoying his football, it will be as hard to prise him away mid-season from Rangers' promotion challenge as it will be for the Scottish side to sell, but that is not to say either Wednesday or Reading, both in need of a striker, will not try.