Marcelo Bielsa fears Leeds' growing injury list could bite when the Championship pacesetters head to Millwall on Saturday.
Striker Patrick Bamford has been ruled out for four months, joining an injury list which has already featured Pablo Hernández and Kemar Roofe, as well as Gaetano Berardi and Jamie Shackleton.
"If we look back, we didn't have many injured players, especially in the same positions, so I can't deny it will be difficult," Bielsa said.
"Now we will see how good the work is that we have done in building the group."
Leeds remain unbeaten with four wins and two draws from their opening six games, but Bielsa is wary of a visit to the Den, comparing the challenge to that of facing fellow unbeaten side Middlesbrough before the international break - a match which finished goalless.
"Millwall are a team who have players who have played at the club for a long time," he said.
"They have a style and we will face similar difficulties that we faced against Middlesbrough."
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