Cooper picked up a muscle strain in the build up to Leeds’ last match against Sheffield Wednesday, which forced Gaetano Berardi to slot into the heart of the Whites’ defence.
The hope was that Leeds’ captain would be back fit again by the weekend.
However, the centre-back has still not fully recovered, and Bielsa was making no promises about him featuring.
Even though Cooper fit, Leeds managed to keep a clean sheet in their last match against Wednesday.
"I cannot say he is definitely out, but his chances are slim," he said. "Difficult to create a conclusion. Information I give has to be accurate. In this case, it’s not easy to have precision in the answer. I say Cooper is not going to play, but it may not be like this."
The Whites looked very solid at the back as they picked up a vital three points in the race for promotion.
Bielsa has challenged Leeds to win all their remaining fixtures with just four games to play.
If Leeds are they are able to pick up the three points on Friday then it will only further strengthen their place in the top two, as they look to return to the Premier League for the first time since 2004.