Sigurdsson, who arrived at Goodison Park last summer from Swansea City, picked up the injury in Saturday's Premier League victory at home to Brighton and a following examination ruled him out for between six and eight weeks.
That would have meant the 28-year-old midfielder missing the remainder of the campaign but Allardyce says whoever put that time limit on his return will find themselves in a spot of trouble.
Allardyce said: "Hopefully Gylfi's recovery time can be shorter than we expect. Medical staff give a conservative view and you try and beat that.
"It's a blow. It's an unfortunate trauma injury. As a manager and backroom staff, we don't want too many injuries but you can't avoid an injury like this.
"I've always felt it's wrong to tag an injury with time limits. You want to avoid setbacks. If you can get it before then you've done well. We'll look at it in the next two weeks.
"Whoever put out the statement saying eight weeks is getting a b******ing."