The Gabon international has been linked with a switch to Spanish giants Real Madrid as he has often spoken about joining Los Blancos and they are on the lookout for attacking reinforcements in January.
As the two sides prepare to meet in the Champions League on Wednesday night Bosz says he hopes his player stays with him beyond the winter transfer window.
When asked if he would be staying he said: "He is an awful player, very bad ... it's a joke.
"I hope he does not go to Madrid. He has the quality to play for them, but I hope he stays with us."
Dortmund are already out of contention for the next round of the Champions League and their best hope is to qualify for the Europa League by finishing third.