Eghill, aged 28 has been at Wigan Athletic this season but has only made one appearance in LDV Van Trophy game against Nott's County.
"We are a bit light on defenders at the moment." said Warnock
"Steve Yates and Ben Doane are still short of full fitness and we couldn't name another defender on the bench on Saturday."
"Richard will train with us for a week and we will have a look at how he does before deciding on anything."
Edghill was released last February from the Maine Road club where the played their for ten years and has failed to find a new club.
Meanwhile, Neil Warnock is still making enquires into signing Dean Windass from Middlesbrough on a permanent basis. Also ex-Blades striker Adrian Littlejohn has joined South Yorkshire rivals Barnsley on trial.