Leeds United central defender Liam Cooper is injured at the moment.
The Whites will take on Hull at Elland Road in the Championship on Tuesday evening.
The West Yoskshire outfit will head into the match against the Tigers on the back of a 2-0 victory over Huddersfield Town away from home in the league.
Cooper is one of the best and most important players for Leeds, but the 28-year-old central defender did not play against Huddersfield on Saturday due to a calf stain.
Bielsa has suggested that Cooper could miss the game against Hull at Elland Road on Tuesday evening.
Bielsa told Leeds Live about Cooper: “We don’t know. Today, it would have been a risk to play. I don’t think this situation is going to change on Tuesday.”
Leeds are in great form at the moment and are among the favourites to clinch automatic promotion to the Premier League.
The Whites are second in the Championship table at the moment with 43 points from 20 matches, two points behind leaders West Bromwich Albion.