Millwall scored an injury-time equaliser just minutes after missing a penalty to dent 10-man Sheffield United’s automatic promotion hopes.
Gary Madine’s goal looked like it would be enough to win the game for the Blades before the dramatic finish.
With five minutes remaining, John Egan was red-carded for handball but Ben Marshall’s penalty hit the bar.
Millwall continued to press and a 94th-minute diving header from Jake Cooper earned them a vital late point in their relegation battle.
The point was enough for United to move back into second in the Championship, pending the outcome of Leeds United’s later game against Sheffield Wednesday.
Both sides had early chances with the Mark Duffy shooting straight at Millwall keeper David Martin, before Lions captain Alex Pearce spurned an opening from a corner.
The home side were then forced into an early change when defender Chris Basham picked-up an injury.
Manager Chris Wilder opted for a reorganisation of his formation as he sent on striker Gary Madine as the centre-back’s replacement.
The Blades were finding Millwall stubborn to break down but began to find some rhythm, with David McGoldrick curling an effort just over the angle.
Lions defender Cooper was then called into action with a crucial intervention to divert Enda Stevens’ shot behind for a corner.
The second-half started as the first ended with the Blades piling on the pressure in search of the opener, which arrived in the 51st minute when John Fleck sent the ball across the box where on-loan Cardiff City striker Madine was waiting to slot home.
United also lost top scorer Billy Sharp to injury in the second half, with the 23-goal striker replaced by Martin Cranie.
Mahlon Romeo went close with a long-range free-kick for Millwall, but with five minutes of normal time remaining, Egan was shown a straight red for handling a Tom Elliott header on the line.
It looked as if the home side would hang on for the points when Marshall struck his penalty against the bar and over, but there was still time for them to level through Cooper’s header deep into stoppage time.
Despite the result, the Lions dropped one place to 20th and are just two points outside the relegation zone, with five games to play.