The Senegal midfielder, signed for around ??3.5m in the summer from West Ham, was an instant hit at the KC Stadium, scoring four times in his first five appearances for the Tigers earlier this season.
But he has not featured since December 3 due to a knee injury and a planned first-team return against Queens Park Rangers on Saturday has now been shelved.
He hurt the same knee at the start of the week and has been rested since to prevent further aggravation.
“He’s had a slight setback, he had a knock to his knee on Monday and we’ve taken him off it all week,” said manager Steve Bruce.
“He’s had to have precautionary scans and X-rays to see how the injury was and thankfully everything’s okay, but as you can imagine he didn’t want a knock there.
“We don’t think it’s going to be too long, in fact we hope he can be joining in with training in the middle of next week.
“But it’s set him back a week or 10 days so he won’t be available on Saturday.”