Seyi Olofinjana in action against Stoke
The Nigerian international picked up a hamstring injury in the 3-2 defeat of Kenya last week, which saw his country qualify for the 2010 World Cup.
The Tigers midfielder is reported to have told Nigerian radio station Brila FM: "The doctors have said I will be out of action for about four weeks following my injury in Kenya."
Phil Brown today confirmed Olofinjana would miss tomorrow night's clash with Everton, and admitted he was a doubt to travel to the City of Manchester Stadium on Saturday.
But he refused to say how long he would be out for.
It will be a huge blow to Hull City ahead of a series of important matches.
Olofinjana scored a stunning goal against Stoke in the 2-1 win a week last Sunday, and his presence as a midfield anchorman was missed in the 3-3 draw with West Ham.
It had been hoped he and Jimmy Bullard would form the sort of complimentary midfield the Tigers have been crying out for.