Allan, 24, impressed with Alan Stubbs' Hibernian last season, and ended up joining Celtic on a four-year deal back in August 2015, with Ronny Deila swooping to land the highly-rated midfielder.
However, Allan has largely been on the fringes of the Celtic side this season, as competition from players like Scott Brown, Nir Bitton, Tom Rogic and Callum McGregor has left him down the pecking order in Glasgow.
After less than a year at Celtic Park, Allan is already being linked with a move away, as The Scottish Sun report that the likes of Derby County, Nottingham Forest and Queens Park Rangers are all keen on signing Allan during this summer's transfer window.
Intriguingly, the report details how Forest boss Dougie Freedman has been a long-term fan of Allan, dating back to when he was Crystal Palace manager.
It's stated that Freedman has admired his fellow Scot for some time, and even attempted to sign him on loan for Palace from West Bromwich Albion back in September 2012, but couldn't afford the deal and he ended up joining Milton Keynes Dons instead.
Now, with Forest allegedly preparing a move this summer - though it's unclear what their transfer embargo situation will be this summer, which could restrict them to a loan deal - Freedman may finally be able to land his man, and give Allan another chance at success in England, having struggled to make an impact with West Brom.
Would Allan be a good signing for Forest?