The midfielder has not featured since earlier December with a knee injury and Hull hoped to be able to select him for this weekend's game at the KC Stadium.
However, manager Steve Bruce revealed on Friday that the Senegal international has sustained another blow to his knee in training.
"We don't think it will set Mo back too long," he said. "I am hoping he can be back training next week."
Hull come into the game 16th in the table, one point clear of the bottom three, with their 2-0 win over Aston Villa last time out their first victory since New Year's Day.
"It's all to play for," said Bruce. "It's going to go all the way to the wire.
"We're in it and we've just got to win two or three more games."
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