The 34-year-old former West Ham midfielder was signed on a one month contract in October and after two impressive performances for Blues' development side Clark is considering offering Diop another contract.
"I'm considering it all the time. I'm watching how he is getting fitter and fitter, better and better," the Blues boss told the media after Diop scored in a 2-0 win for the development side against Sheffield Wednesday yesterday.
"It's under consideration but we have other things that are priorities at the moment in terms of the games.
"He knows what I am about. We go back a long way.
"He got through the 90-odd minutes on Wednesday and looks like he is getting fitter and stronger."
"He's been very popular around the place. He hasn't entered the field of play yet but you see his demeanour around the place, he lifts everyone.
"After the games when we've had good results he's been so bubbly. He's been a massive boost for everybody. He is getting closer and closer to getting on the field."