Shittu, 29 started his professional career with Charlton Athletic in 2000, but despite a loan move to Blackpool failed to make any appearances for the London club and in January 2002 made the move to Loftus Road after a successful loan spell.
He soon made a name for himself after his £350,000 move - he went onto make over 170 appearances for the Hoops before Watford lured him to the Premier League after their successful promotion. With the Hornets he played alongside Darius Henderson, Marlon King, Steven Kabba and Matthew Spring.
Watford were relegated in their first season but the Nigerian international stayed at Vicarage Road until August 2008 when he made a £2,000,000 move to present club Bolton Wanderers.
However with the introduction of Fabrice Muamba and Gary Cahill the centre-half has found opportunities limited and has yet to feature for the Trotters this season.
It has now emerged that along with Newcastle United and Ipswich Town the Blades are battling for the loan services of Shittu with a £1,500,000 transfer in January.