Match ends, Sheffield United 2, Leyton Orient 2.
Romain Vincelot's last-gasp header snatched 10-man Leyton Orient a point after a dramatic finish against Sheffield United.
The visitors had taken a first-half lead through Jay Simpson, before Jobi McAnuff was sent off after the break.
The Blades had to wait until the 90th minute to equalise through Paddy McCarthy and then Marc McNulty's header looked to have won it.
However, deep into added time, Vincelot headed in from a corner to earn a draw.
The Frenchman's equaliser maintains Leyton Orient's unbeaten away record this season, but they were ahead until the final minute of normal time.
The hosts should have taken an early lead but Jose Baxter fired wide, and Orient punished them with a goal against the run of play.
Simpson, who scored a midweek brace against Dagenham & Redbridge in the Football League Trophy, netted his first league goal of the season, slotting home from close range after Mark Howard had parried.
After McAnuff was dismissed for a second bookable offence, Orient posed little threat going forward.
Instead, the hosts piled on the pressure, McNulty seeing a goal disallowed for offside before Chris Basham's effort hit the crossbar.
The visitors' resistance finally broke down when McCarthy nodded home and the Blades thought they had earned a fourth consecutive home win after McNulty's header.
But with seven minutes of injury time being played, a Jack Price corner was nodded in by Vincelot, much to the delight of caretaker manager Kevin Nugent.
Leyton Orient manager Kevin Nugent told BBC London 94.9:
"They started really well against us but we got better and better in the first half.
"In the second half we got camped in. We thought we may have lost it but we got back into it - it was a real up-and-down afternoon.
"We seem to be able to deal with the away games better at the moment but we will be looking to change that."
Nugent on management situation:
"The situation is not that much different to what it was before. The club will be making a statement shortly on the current situation."
- 2AlcockBooked at 74mins
- 4WallaceSubstituted forCampbell-Ryceat 72'minutes
- 10ScougallSubstituted forBashamat 74'minutes
- 11BaxterSubstituted forMcNultyat 61'minutes
- 33WoodsBooked at 89mins
- 15ClarkeBooked at 42mins
- 18PritchardSubstituted forBattat 90+3'minutes
- 26PriceBooked at 90mins
- 27SimpsonSubstituted forDagnallat 69'minutes
- 24HendersonBooked at 78minsSubstituted forBartleyat 84'minutes
- 11McAnuffBooked at 75mins
- Andy Haines
- Shots on Target
Second Half ends, Sheffield United 2, Leyton Orient 2.
Goal! Sheffield United 2, Leyton Orient 2. Romain Vincelot (Leyton Orient) header from the centre of the box to the high centre of the goal.
Corner, Leyton Orient. Conceded by Robert Harris.
Foul by Craig Alcock (Sheffield United).
Shane Lowry (Leyton Orient) wins a free kick on the left wing.
Foul by Robert Harris (Sheffield United).
Romain Vincelot (Leyton Orient) wins a free kick in the defensive half.
Substitution, Leyton Orient. Shaun Batt replaces Bradley Pritchard.
Jack Price (Leyton Orient) is shown the yellow card.
Goal! Sheffield United 2, Leyton Orient 1. Marc McNulty (Sheffield United) header from the centre of the box to the top right corner.
Corner, Sheffield United. Conceded by Shane Lowry.
Goal! Sheffield United 1, Leyton Orient 1. Paddy McCarthy (Sheffield United) right footed shot from the centre of the box to the high centre of the goal.
Gary Woods (Leyton Orient) is shown the yellow card.
Marc McNulty (Sheffield United) hits the bar with a header from very close range.
Hand ball by Shane Lowry (Leyton Orient).
Attempt blocked. Jay McEveley (Sheffield United) right footed shot from outside the box is blocked.
Attempt saved. Marc McNulty (Sheffield United) right footed shot from the right side of the six yard box is saved in the bottom right corner.
Corner, Sheffield United. Conceded by Elliot Omozusi.
Substitution, Leyton Orient. Marvyn Bartley replaces Darius Henderson.