Clarke has been out of action since going down with an illness that hospitalised him halfway through the Whites' game against Middlesbrough last month but he could be in line for a return to action against the Blades this weekend.
Leeds currently sit at the top of the Championship but could be leapfrogged by their Yorkshire rivals if they lose on Saturday.
Bielsa is thinking about recalling one of his star players for the crucial clash but the manager is keeping his cards close to his chest on this occasion.
When asked whether Clarke was ready to feature against Sheffield United, Bielsa told the Yorkshire Evening Post: “I haven’t taken my decision yet.”
Bielsa’s starting side has been unchanged for five consecutive matches and many expect the Leeds head coach to field the same line-up against Sheffield United but there could be some more injury returnees.
Top scorer Kemar Roofe has been working to shake off a knee injury whilst Adam Forshaw is battling to be fit for the game against Chris Wilder's side.
The Championship leaders will be desperate to have a full-strength side in a game that could decide the fate of their entire season.
One man who will feel fortunate to line up on Saturday is Luke Ayling. The full-back was lucky to not see red for a poor challenge on Mo Barrow against Reading on Tuesday night after already picking up a yellow card in the game.
Bielsa said: “This is up to the referee and I don’t make comments on referees. If we take into account your question, we could think the referee could have taken another decision.
“But when he (Ayling) made the tackle it was not with a bad intention. His intention was not to interrupt the action of the player.”
Leeds' form suffered a dip at the beginning of 2019 but their recent resurgence has seen them hold onto a spot in the top two although they face one of their toughest tests this weekend, Sheffield United have been in red-hot form and the winner of this could be the team that ends up playing Premier League football next season.