TEN MAN Orient salvaged a point after it looked like they had let three fall through their fingers in a dramatic finale at Bramall Lane.
Orient had led for the whole of the second half after Jay Simpson's opener before Jobi McAnuff was sent off with 15 minutes remaining. The home side put Orient right up against it and looked like they had won it through goals from Paddy McCarthy and Marc McNnulty late on but in the eighth minute of stoppage time Romain Vincelot rose highest to thump home a header and salvage a point for the O's.
Kevin Nugent kept a similar shape to the one which worked well at Dagenham with Darius Henderson spearheading a forward three against his former club, flanked by Jobi McAnuff and Jay Simpson.
Jack Price made his debut anchoring a midfield three behind Romain Vincelot and Bradley Pritchard as Dean Cox missed the trip with a knee problem.
At the back, Mathieu Baudry failed to recover from a hamstring strain which forced him off against Dagenham on Tuesday as Shane Lowry took his place.
The sides last met a fortnight ago in the Capital One Cup, the Blades took an early lead that night and almost did again when good work on the right created an opening from Jose Baxter in the first minute but he dragged a shot wide when he should have scored.
Orient recovered to force a couple of early corners that caused problems but with seven gone they were indebted to Scott Cuthbert who did well to slide and stop Jamie Murphy's shot as the home side looked to counter.
The early flurry of action led to a far more placid spell as both sides prodded and probed in midfield without either goalkeeper really being called into action.
With the half seeming to drift towards its conclusion, Orient shattered the deadlock as Jay Simpson poached his third goal in two games.
Omozusi swung a deep ball in from the left that Pritchard challenged for and managed to steer across the face for Simpson to smash home from close range.
Having grabbed one, the O's almost double their lead a minute later when Jobi McAnuff found a way in down the right but his dangerous cross was scrambled away for a corner.
The goal seemed to sour the mood of the home fans as the atmosphere seemed more sour with grumblings of discontent rife, as the fans shuffled down the stairs for a half time cuppa.
The home side came out of the blocks with more purpose as Craig Alcock had a header cleared off the line by Simpson in the opening couple of minutes before James Wallace came up with a contender for miss of the season.
Jose Baxter fizzed in a cross from the right that Lowry deflected against his own post. With Gary Woods beaten all Wallace had to do was turn it from a yard out but managed to balloon his effort over the bar.
The wind was firmly in the sails of the home side as Orient were pegged back deeper and deeper and struggled to get hold of the ball.
Marc McNulty went close with a header before Nugent shuffled his pack and brought on Chris Dagnall in place of the goal scorer Simpson.
The game came alive again with 15 minutes to play when McAnuff received his marching orders for a second yellow after a late tackle on Alcock.
Orient shifted to a 4-4-1 formation and a minute later thought they had been pegged back when McNulty turned home at the back post but the flag was up for offside.
It really was backs against the wall stuff for the O's as they survived a penalty appeal two minutes later as the Blades set themselves up for an onslaught on the Orient goal in the last 10 minutes.
Substitute Jamal Campbell-Ryce started to terrorise the O's and his cross with five minutes to go sparked an almighty scramble as the ball hit the post and somehow stayed out before Basham headed against the woodwork a minute later.
The leveller was coming though and with time ticking away Paddy McCarthy grabbed it when he pounced on a loose ball to smash home from six yards, though Orient were enraged as it looked like Vincelot had been fouled in the build up.
Orient were on the ropes and didn't have to wait long for what looked like the knock-out blow from the Blades. It came again from another cross from the right and this time Marc McNulty rose highest to head home thinking he had won it for the home side.
There would be one more twist in the tale though as Orient won a corner in what was the last chance saloon and when Price picked out Vincelot the Frenchman made no mistake to smash a header home to grab his fourth goal of the season.
ORIENT: Woods, Omozusi, Vincelot, Cuthbert, McAnuff, Lowry, Clarke (C), Pritchard (Batt 90), Henderson (Bartley 84), Price, Simpson (Dagnall 69)
SUBS: Batt, Lee, Kashket, Grainger, Ling
Goals: Simpson 38, Vincelot 90
Bookings: Clarke 42, Henderson 78, Woods 89, 90 Prichard/Price
Red: McAnuff (two yellows: 40 and 74)
SHEFF UTD: Howard, Alcock, Harris, Wallace (Campbell-Ryce 71), Flynn, Doyle (C), Murphy, Scougall (Basham 74), Baxter (McNulty 61), McEveley, McCarthy
SUBS: Davies, McGahey, Reed, Turner
Goals: McCarthy 90, McNulty 90
Bookings: Alcock 73
Ref: A. HAINES
Attendance: 19,179 (599)