The Yorkshire outfit journey to north London unbeaten in six league games to retain their top-flight status - which was confirmed following West Ham United's defeat to Arsenal on Sunday afternoon - with in-form attacker Okafor playing a big part in their recent success.
The Swiss forward scored in their 3-1 home win over Burnley last time out to take his league tally to eight this term but picked up a calf strain in that fixture which will keep him out for two games.
Gudmundsson has been the first choice at either left-back and left wing-back throughout his 32 top-flight appearances but was ruled out against the Clarets and won't have recovered in time for tonight's game.
Meanwhile, there is a doubt over central defender Pascal Struijk who missed training on Friday with a hip contusion although they are hopeful he'll be fit to make the trip.