McAllister, who has had limited opportunities to shine in recent months, is set to join The Stags for a month in a bid to get him experience and some valuable first-team opportunities under his belt.
Mansfield take on Peterborough at the weekend and the 20-year-old, who has one Owls goal to his name, will be hoping to be involved.
In other news, star player Whelan has been reported to be on the verge of a loan move to Stoke City with a view to a permanent move.
There is no official comment on this rumour but if the former Ireland Under-21 skipper leaves Hillsborough there will be many questions asked - especially after the club has seen it's three star players in Madjid Bougherra, Steve MacLean and Chris Brunt leave S6 this year.
Brian Laws has also been linked with Tranmere's 19-year-old prospect Steven Davies, a winger who has also attracted the interest of Leeds and Wolves.