The 25 year-old forward has previously been linked with Burnley, who are apparently unwilling to pay the £1m transfer fee that Celtic are demanding for the ex-Hibs man.
Whilst at Easter Road, Riordan bagged 54 goals in 123 appearances which earnt him a move to Celtic for £200,000 following a clause in the Scot's contract.
This, coupled with the news that Darren Moore is set to complete a move to Barnsley would signify Patrick Cryne's intent to spend big to earn the Reds a higher placing in the Championship next season, starting in just 41 days!!!