Sheffield United top goalscorer Billy Sharp was forced with an injury as the Blades failed to beat Millwall at Bramall Lane on Saturday afternoon.
Former Whites man Sharp was substituted with 64 minutes on the clock with reports suggesting he has pulled a hamstring and he appears to be a doubt for the final run-in the Championship.
The 33-year-old has been in superb form for the Blades this season with 23 goals and his possible absence would be a major blow to Chris Wilder's chances of beating Leeds United to automatic promotion.
Sheffield United had looked set to take all three points after Gary Madine's second half goal.
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But they were reduced to ten men on 85 minute when John Egan handled on the line and despite Millwall missing the resulting penalty, the Lions struck deep in added time through Jake Cooper.
Egan will now serve a suspension after his red card while Chris Basham also went off with an injury in the first half on a tough day for the Blades.
Leeds United take on Sheffield Wednesday in the teatime kick-off in the Championship, knowing they can extend their lead to two-points on the South Yorkshire side.
