Sheffield United and nine-man Brentford played out a thrilling draw.
Marcello Trotta's penalty put the Bees ahead before Tony Craig was sent off for violent conduct in the area.
Tony McMahon hit the bar from the resulting spot-kick but the Blades went in front through Barry Robson's penalty and Dave Kitson's header.
Sam Saunders then had a penalty saved and home defender Harry Maguire and Clayton Donaldson were shown red before Bradley Wright-Phillips equalised.
The two teams, sitting fifth and third before kick-off, entered the game knowing that a win would be key to their chances of gaining automatic promotion from League One.
In a scrappy opening it was the hosts who had the better of the chances with Brentford keeper Simon Moore saving well from Kevin McDonald and Michael Doyle in quick succession.
Uwe Rosler's side went ahead when Donaldson raced away from the Blades defence and poked beyond George Long before being taken out by the teenager and Fulham loanee Trotta confidently hammered the resultant penalty down the middle.
The hosts pressed for an equaliser before the interval but McDonald volleyed over and a contentious first half, eight bookings giving an indication of what was to follow, ended with the Bees in front.
Visiting skipper Craig saw red early in the second half for an off-the-ball altercation with Kitson in the area but the Blades were unable to make the most of the situation, with McMahon hitting the bar with his spot-kick.
They did not have to wait long for another opportunity to level the scores however, Lee Hodson penalised for handball and this time Robson stepped up to smash his penalty in off the woodwork.
Kitson headed the hosts ahead from Jamie Murphy's centre before Maguire saw red for the Blades for fouling Donaldson in the area.
Long got down brilliantly to keep out Saunders' spot-kick and minutes later Donaldson, booked in the first half for diving, was following Craig and Maguire down the tunnel for a second yellow.
Just when it looked like the Blades would hold out to secure successive wins under caretaker boss Chris Morgan, Brentford sub Wright-Phillips sprinted beyond the tired home defence to coolly slot home.
The draw leaves Brentford one point behind second-placed Bournemouth while Sheffield United, who have a game in hand on the rest of the top six, are four points further back.
VIEW FROM THE DRESSING ROOM
Sheffield United caretaker-manager Chris Morgan told BBC Radio Sheffield:
"It was just a crazy game of football.
"A lot of bookings, three sending offs, four penalties and I don't even think it was a dirty game.
"It's hard to take, because we get our noses in front after being 1-0 down, were 2-1 up and they're down to nine men. You'd expect us to see it out, but the unity and team spirit to get back in the game is the most pleasing thing."
Live Text Commentary
Full Time The referee blows for the end of the match.90:00 +5:51
The ball is crossed by Barry Robson, save made by Simon Moore.90:00 +4:48
Free kick awarded for an unfair challenge on Jake Reeves by Kevin McDonald. Harlee Dean takes the free kick.90:00 +3:10
Tony McMahon takes a shot. Simon Moore makes a brilliant save. Tony McMahon takes a shot. Save by Simon Moore.90:00 +2:39
Tony McMahon produces a cross.90:00 +0:01
Free kick awarded for a foul by Jonathan Forte on Shaleum Logan. Simon Moore takes the indirect free kick.88:40
Assist by Kevin O'Connor.88:40 Goal scored
Goal! - Bradley Wright-Phillips - Sheff Utd 2 - 2 Brentford Bradley Wright-Phillips finds the back of the net with a goal from inside the penalty area to the bottom right corner of the goal. Sheff Utd 2-2 Brentford.87:36
Bradley Wright-Phillips takes a shot. Danny Higginbotham gets a block in. Corner taken by Sam Saunders from the left by-line, Close range header by Harlee Dean misses to the right of the target.86:54
Jamie Murphy is flagged offside by the assistant referee. Simon Moore restarts play with the free kick.83:30
Barry Robson produces a cross, blocked by Shaleum Logan. Corner taken short by Jamie Murphy.81:53
Jonathan Forte concedes a free kick for a foul on Jake Reeves. The free kick is swung in right-footed by Sam Saunders, clearance by Kevin McDonald.81:20
Chris Porter is penalised for a handball. Kevin O'Connor takes the indirect free kick.80:39
Free kick taken by Matthew Hill.80:39 Booking
Booking Booking for Shaleum Logan for unsporting behaviour.79:57
Jake Reeves takes a shot. George Long makes a brilliant save. Toumani Diagouraga takes a short corner, free kick awarded for an unfair challenge on Jamie Murphy by Shaleum Logan.78:16
Barry Robson challenges Sam Saunders unfairly and gives away a free kick. Free kick taken by Simon Moore.76:42
Direct free kick taken by Barry Robson.76:42 Dismissal
Dismissal The referee shows Clayton Donaldson a red card.76:13
Clayton Donaldson challenges Kevin McDonald unfairly and gives away a free kick.
Substitution (Sheff Utd) makes a substitution, with Danny Higginbotham coming on for Dave Kitson.72:36
George Long restarts play with the free kick.72:36 Substitution
Substitution (Brentford) makes a substitution, with Bradley Wright-Phillips coming on for Marcello Trotta.72:36
George Long fouled by Marcello Trotta, the ref awards a free kick.72:36 Penalty
A save by George Long from penalty by Sam Saunders. Sheff Utd 2-1 Brentford.71:42 Dismissal
Dismissal Red card for Harry Maguire.71:13
Harry Maguire challenges Clayton Donaldson unfairly and gives away a Penalty.68:47
Clayton Donaldson takes a shot. Clearance by Matthew Hill.67:01 Substitution
Substitution Sam Saunders comes on in place of Adam Forshaw.67:01
Assist on the goal came from Jamie Murphy.67:01 Goal scored
Goal! - Dave Kitson - Sheff Utd 2 - 1 Brentford Dave Kitson finds the back of the net with a headed goal from close in. Sheff Utd 2-1 Brentford.66:18
Tony McMahon produces a cross, Harlee Dean manages to make a clearance.65:08
Handball decision goes against Adam Forshaw. Free kick taken by Dave Kitson.65:08 Substitution
Substitution Kevin O'Connor on for Lee Hodson.61:49
Unfair challenge on Adam Forshaw by Matthew Hill results in a free kick. Jake Reeves takes the indirect free kick. Handball by Dave Kitson. Jake Reeves shoots direct from the free kick, Simon Moore makes a save. Corner taken left-footed by Jake Bidwell, clearance made by Tony McMahon.61:49 Goal scored
Goal! - Barry Robson - Sheff Utd 1 - 1 Brentford Penalty taken left-footed by Barry Robson and scored. Sheff Utd 1-1 Brentford.59:49
Tony McMahon takes a shot. Lee Hodson gets a block in. Barry Robson takes a shot. Blocked by Jake Reeves. Inswinging corner taken from the left by-line by Jamie Murphy. Handball by Lee Hodson.59:18
The referee gives a free kick against Jake Reeves for handball. Harry Maguire takes the indirect free kick.58:54
Free kick awarded for a foul by Tony McMahon on Adam Forshaw. Simon Moore restarts play with the free kick.58:15 Substitution
Substitution Barry Robson comes on in place of Michael Doyle.58:02
Kevin McDonald produces a right-footed shot from inside the area that clears the bar.57:30
Inswinging corner taken right-footed by Jamie Murphy, Harlee Dean manages to make a clearance.56:14
Inswinging corner taken by Jake Reeves from the left by-line, clearance made by Matthew Hill.54:05
Jonathan Forte delivers the ball, Clayton Donaldson manages to make a clearance. A cross is delivered by Tony McMahon, save made by Simon Moore.52:38
Unfair challenge on Simon Moore by Chris Porter results in a free kick. Free kick taken by Simon Moore.50:28
Effort on goal by Chris Porter from inside the penalty area goes harmlessly over the bar.50:28 Penalty
Penalty missed by Tony McMahon.50:28
Tony Craig concedes a Penalty for a foul on Dave Kitson.50:28 Dismissal
Dismissal The referee shows Tony Craig a red card.49:29
The ball is swung over by Adam Forshaw, George Long makes a save.47:43
Jamie Murphy takes a shot.45:34
Shaleum Logan challenges Jamie Murphy unfairly and gives away a free kick. Indirect free kick taken by George Long.45:01
The referee blows his whistle to start the second half.45:01 Substitution
Substitution Ryan Flynn goes off and Jonathan Forte comes on.45:00 +4:29 Half time
Half Time The half-time whistle blows.45:00 +3:27
Direct free kick taken by Jake Reeves. The ball is crossed by Marcello Trotta, George Long makes a clearance. Inswinging corner taken right-footed by Jake Reeves, Kevin McDonald makes a clearance.45:00 +3:27 Booking
Booking Tony McMahon is cautioned.45:00 +3:18
Unfair challenge on Clayton Donaldson by Tony McMahon results in a free kick.45:00 +1:50
Foul by Kevin McDonald on Adam Forshaw, free kick awarded. Free kick taken by Jake Reeves.44:54 Booking
Booking Booking for Clayton Donaldson for unsporting behaviour.44:12
Unfair challenge on Harry Maguire by Marcello Trotta results in a free kick. Harry Maguire takes the free kick.43:05
Chris Porter delivers the ball, blocked by Jake Reeves. Outswinging corner taken by Tony McMahon from the right by-line, Harlee Dean manages to make a clearance. Effort on goal by Ryan Flynn from just inside the penalty area goes harmlessly over the target.40:46
Michael Doyle is penalised for handball and concedes a free kick. Shot on goal comes in from Jake Reeves from the free kick, save by George Long.39:48
Corner taken by Tony McMahon, Dave Kitson has a headed effort at goal from deep inside the area missing to the left of the target.38:55
Corner taken by Tony McMahon from the left by-line, Simon Moore makes a save.37:49
Matthew Hill takes the indirect free kick.37:49 Booking
Booking Michael Doyle is shown a yellow card for dissent.37:38
Free kick awarded for an unfair challenge on Matthew Hill by Lee Hodson.36:19
Inswinging corner taken by Jake Reeves, Marcello Trotta takes a shot. Save by George Long.34:05
Matthew Hill concedes a free kick for a foul on Lee Hodson. Free kick taken by Jake Reeves. Corner taken by Jake Reeves, Chris Porter manages to make a clearance.33:11
Clayton Donaldson fouled by Tony McMahon, the ref awards a free kick. Free kick taken by Jake Bidwell.32:01
Inswinging corner taken from the left by-line by Tony McMahon, Harry Maguire has an effort at goal from deep inside the area missing to the right of the target.31:09
Toumani Diagouraga challenges Michael Doyle unfairly and gives away a free kick. Tony McMahon takes the free kick.28:36
Harry Maguire concedes a free kick for a foul on Marcello Trotta. Tony Craig restarts play with the free kick.28:00
The ball is swung over by Kevin McDonald, clearance by Jake Bidwell.27:38 Booking
Booking Dave Kitson goes into the book.27:33 Booking
Booking Booking for Jake Reeves for unsporting behaviour.26:27
Marcello Trotta gives away a free kick for an unfair challenge on Harry Maguire. Indirect free kick taken by George Long.25:51
Shaleum Logan crosses the ball, clearance by Tony McMahon.25:05
Free kick crossed right-footed by Jake Reeves, save by George Long.25:05 Booking
Booking The referee cautions Harry Maguire for unsporting behaviour.24:48
Harry Maguire gives away a free kick for an unfair challenge on Clayton Donaldson.23:53 Goal scored
Goal! - Marcello Trotta - Sheff Utd 0 - 1 Brentford Marcello Trotta scores a power penalty. Sheff Utd 0-1 Brentford.23:34 Booking
Booking Caution for George Long.22:43
Clayton Donaldson fouled by George Long, the ref awards a Penalty.22:14 Booking
Booking Simon Moore goes into the referee's book for time wasting.21:44
Effort on goal by Michael Doyle from inside the penalty area goes harmlessly over the bar.19:08
Clayton Donaldson takes a shot from just outside the penalty area clears the crossbar.18:26
The assistant referee signals for offside against Chris Porter. Free kick taken by Simon Moore.17:55
Jamie Murphy crosses the ball, clearance by Harlee Dean.15:36
Corner taken by Tony McMahon from the left by-line, clearance made by Jake Reeves. Volleyed left-footed shot by Michael Doyle. Save made by Simon Moore. Corner from the left by-line taken by Tony McMahon, clearance made by Tony Craig.15:16
Kevin McDonald takes a shot. Save made by Simon Moore.14:42
Matthew Hill fouled by Lee Hodson, the ref awards a free kick. Neill Collins takes the free kick.13:48
A cross is delivered by Ryan Flynn, Shot from just outside the box by Chris Porter goes over the bar. Harlee Dean manages to make a clearance.13:23
Centre by Jamie Murphy, clearance made by Harlee Dean.11:37
Jake Reeves fouled by Dave Kitson, the ref awards a free kick. Free kick taken by Tony Craig.9:51
Corner taken right-footed by Jake Reeves, Lee Hodson takes a shot. Kevin McDonald gets a block in. Short corner taken by Jake Reeves from the right by-line. Foul by Marcello Trotta on Neill Collins, free kick awarded. George Long takes the free kick.9:04
Dave Kitson challenges Toumani Diagouraga unfairly and gives away a free kick. Harlee Dean takes the free kick.7:59
The ball is delivered by Adam Forshaw, save made by George Long.6:06
Free kick awarded for a foul by Michael Doyle on Marcello Trotta. Tony Craig takes the indirect free kick.5:22
Foul by Jake Reeves on Kevin McDonald, free kick awarded. Free kick taken by George Long.2:48
Free kick awarded for an unfair challenge on Jake Reeves by Dave Kitson. Jake Reeves restarts play with the free kick.1:56
Ryan Flynn challenges Lee Hodson unfairly and gives away a free kick. Indirect free kick taken by Simon Moore.0:33
Adam Forshaw gives away a free kick for an unfair challenge on Michael Doyle. Matthew Hill takes the free kick.0:00
The referee starts the match.
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