Peterborough United climbed out of the Championship relegation zone on goal difference as they eased past Derby County to earn a fourth win in six.
Michael Bostwick netted from close range to make it 1-0 before the break.
Rams keeper Adam Legzdins saved Lee Tomlin's second-half penalty, but the visitors' hopes of extending a five-game unbeaten run were hit when Jake Buxton was sent off.
And two late long-range strikes from Saido Berahino wrapped up the win.
The margin of victory would have been bigger but for an inspired display by Legzdins.
He made a series of fine saves to keep Derby in the game until his unfortunate mistake all but ended their chances on 86 minutes when he allowed Berahino's shot to slip through his grasp.
Derby started well enough and defender Richard Keogh headed wide from Paul Coutts' corner early on while on-loan West Brom striker Berahino went close for the hosts with a right-foot shot.
But Posh began to get on top. They went ahead after half an hour when Bostwick blasted an effort into the top right-hand corner and Legzdins then pulled off fine saves to deny George Boyd and Berahino.
Conor Sammon went close to drawing Derby level but shot wide from six yards and Theo Robinson then went even closer after the interval when his 12-yard shot hit a post.
Tomlin should have put Peterborough 2-0 in front in the 57th minute after Keogh brought down Boyd but Legzdins saved the spot-kick.
Buxton's second booking inside four minutes for fouls on Berahino and then Boyd left Derby facing an even more difficult task.
Legzdins produced more heroics to keep out a Bostwick shot and parry an effort from substitute Danny Swanson, but he undid some of his good work with four minutes remaining when he dropped Berahino's 18-yard strike shot over his own goalline.
Win or bust for Posh
Peterborough have yet to draw a Championship fixture this season, losing their first seven matches but winning four of their last six.
And Berahino added a third deep into injury time when he raced clear and beat Legzdins.
Peterborough United manager Darren Ferguson:
"Saido is only 19 but he is already a very good player. He is intelligent, caused Derby problems all afternoon and fully deserved his goals.
"We have already asked the question about whether we can extend the loan to the end of the season.
"Saido is loving life here and Steve Clarke, the West Brom manager, knows he is being well looked after.
"We've won four of our last six matches and the players deserve an awful lot of credit for showing real bottle in a tough situation.
"Some people were already thinking we were down and out and there were a lot of tough questions being asked, but we have showed what we are capable of doing when playing to the right standard."
Derby County manager Nigel Clough:
"It was one of those games where everything that could do wrong did.
"We felt Jake was unlucky to be sent off as it looked like he won the ball before making contact with the player when picking up his second yellow card, but it is difficult to criticise a referee when your team has just lost 3-0.
"The final scoreline might be a tad harsh but you can't really have too many complaints when making the sort of errors we did for two of the Peterborough goals.
"We also had as good a chance to get back into a game as you will ever see when Theo hit the post, but we couldn't take it.
"I'm just glad Adam's error for the second goal wasn't a game-changing moment because, just like in recent games, he had been outstanding."
- 01 Olejnik
- 03 Alcock
- 04 Brisley
- 19 Little
- 24 Ntlhe
- 06 Bostwick Booked
- 11 McCann
- 20 Knight-Percival
- 08 Tomlin (Sinclair - 80' )
- 10 Boyd Booked (Swanson - 75' )
- 38 Berahino
- 26 Richardson
- 05 Zakuani
- 07 Swanson
- 17 Newell
- 18 Ferdinand
- 09 Barnett
- 12 Sinclair
- 13 Legzdins
- 02 Brayford
- 03 Roberts (Tyson - 80' )
- 05 Buxton Dismissed after an earlier booking
- 06 Keogh Booked
- 07 Coutts
- 08 Hendrick (O'Connor - 84' )
- 12 Jacobs (O'Brien - 72' )
- 19 Hughes
- 11 Robinson
- 32 Sammon
- 30 Deeney
- 15 O'Brien
- 16 O'Connor
- 23 Freeman
- 18 Davies
- 09 Tyson
- 20 Bennett
Live Text Commentary
Full Time The final whistle goes and the game is over.90:00 +5:08
Assist by Kgosi Ntlhe.90:00 +5:08 Goal scored
Goal! - Saido Berahino - Peterboro 3 - 0 Derby Saido Berahino finds the back of the net with a goal from the edge of the area to the bottom right corner of the goal. Peterborough 3-0 Derby.90:00 +4:51
The ball is delivered by Nathan Tyson, Nathaniel Knight-Percival manages to make a clearance.90:00 +4:09
James O'Connor handles the ball and concedes a free kick. Free kick taken by Nathaniel Knight-Percival.90:00 +2:17
Saido Berahino concedes a free kick for a foul on Will Hughes. Paul Coutts takes the free kick.90:00 +0:57
Mark Little takes a shot. Save made by Adam Legzdins.89:25
Danny Swanson takes a shot. Blocked by Mark O'Brien. Corner taken short by Grant McCann.88:22
Foul by Mark Little on John Brayford, free kick awarded. Richard Keogh restarts play with the free kick.85:20 Goal scored
Goal! - Saido Berahino - Peterboro 2 - 0 Derby Saido Berahino grabs a goal from just outside the penalty box to the bottom right corner of the goal. Peterborough 2-0 Derby.83:59 Substitution
Substitution James O'Connor joins the action as a substitute, replacing Jeff Hendrick.83:30
Danny Swanson takes a shot. Save by Adam Legzdins.82:16
Jeff Hendrick gives away a free kick for an unfair challenge on Saido Berahino. Nathaniel Knight-Percival takes the free kick.80:16
Corner from the right by-line taken by Grant McCann, save by Adam Legzdins.79:04 Substitution
Substitution Emile Sinclair comes on in place of Lee Tomlin.79:04 Substitution
Substitution Nathan Tyson is brought on as a substitute for Gareth Roberts.78:39
Will Hughes sends in a cross, clearance by Kgosi Ntlhe.76:16
Will Hughes takes a shot. Shaun Brisley gets a block in.74:59 Substitution
Substitution Danny Swanson replaces George Boyd.73:37
Corner taken left-footed by Grant McCann from the left by-line to the near post, save made by Adam Legzdins.
Corner taken by Grant McCann from the right by-line, Theo Robinson makes a clearance. Mark Little takes a shot. Clearance by Jeff Hendrick.69:57
The ball is crossed by Grant McCann, Michael Bostwick takes a shot. Save by Adam Legzdins.69:57 Substitution
Substitution Mark O'Brien comes on in place of Michael Jacobs.69:57 Dismissal
Dismissal The referee sends off Jake Buxton for second bookable offence.69:40
George Boyd fouled by Jake Buxton, the ref awards a free kick.67:10
Effort on goal by George Boyd from just inside the penalty box goes harmlessly over the target.65:48
Grant McCann produces a shot on goal direct from the free kick.65:48 Booking
Booking Jake Buxton shown a yellow card.65:41
Free kick awarded for a foul by Jake Buxton on Saido Berahino.62:42
Jake Buxton takes the direct free kick.62:42 Booking
Booking The referee cautions Michael Bostwick for unsporting behaviour.62:36
Free kick awarded for a foul by Michael Bostwick on Will Hughes.62:08
The ball is crossed by Conor Sammon, Craig Alcock gets a block in.60:32
The referee blows for offside against Jeff Hendrick. Robert Olejnik takes the indirect free kick.60:17
The ball is delivered by Will Hughes.59:56
Short corner worked by Michael Jacobs.58:33
The ball is delivered by Saido Berahino, clearance made by Gareth Roberts.57:29
Shaun Brisley concedes a free kick for a foul on Theo Robinson. Free kick taken by Will Hughes.57:05
Short corner worked by Grant McCann.56:47 Penalty
A save by Adam Legzdins from penalty by Lee Tomlin. Peterborough 1-0 Derby.55:57 Booking
Booking The referee books Richard Keogh for unsporting behaviour.55:24
George Boyd fouled by Richard Keogh, the ref awards a Penalty.51:08
The ball is delivered by Theo Robinson, clearance by Grant McCann.49:29
Centre by John Brayford, Theo Robinson produces a right-footed shot from deep inside the penalty area and strikes the post.49:12
Michael Bostwick concedes a free kick for a foul on Will Hughes. Will Hughes restarts play with the free kick.48:22
Saido Berahino sends in a cross, clearance by Richard Keogh.47:27
Free kick awarded for an unfair challenge on Grant McCann by Conor Sammon. Direct free kick taken by Grant McCann.46:29
Theo Robinson has an effort at goal from just outside the box which goes wide of the right-hand post.45:01
The referee blows his whistle to start the second half.45:00 +4:04 Half time
Half Time The referee calls an end to the first half.45:00 +3:03
The ball is delivered by John Brayford, Conor Sammon takes a shot. Comfortable save by Robert Olejnik.45:00 +1:17
Michael Jacobs takes a shot. Save made by Robert Olejnik.44:49
Lee Tomlin concedes a free kick for a foul on Will Hughes. Michael Jacobs produces a shot on goal direct from the free kick.43:20
Will Hughes gives away a free kick for an unfair challenge on George Boyd. Direct free kick taken by Grant McCann.42:03
Centre by Nathaniel Knight-Percival, save made by Adam Legzdins.41:05
Centre by Lee Tomlin, Richard Keogh makes a clearance.40:06
Mark Little takes a shot. Richard Keogh gets a block in. Corner taken left-footed by Grant McCann, Kgosi Ntlhe takes a shot. Save made by Adam Legzdins.39:33
Conor Sammon produces a right-footed shot from deep inside the six-yard box which goes wide of the left-hand post.38:52
The ball is sent over by John Brayford.37:56
Shot from long distance by George Boyd misses to the right of the target.36:18
Conor Sammon challenges Shaun Brisley unfairly and gives away a free kick. Grant McCann takes the free kick.34:07
Paul Coutts crosses the ball in from the free kick, Kgosi Ntlhe manages to make a clearance.34:07 Booking
Booking George Boyd goes into the book for unsporting behaviour.33:30
George Boyd concedes a free kick for a foul on John Brayford.32:12
Corner taken left-footed by Grant McCann from the right by-line to the near post, free kick awarded for a foul by Saido Berahino on Adam Legzdins. Direct free kick taken by Adam Legzdins.31:53
Saido Berahino takes a shot. Save made by Adam Legzdins.31:33
George Boyd takes a shot. Save made by Adam Legzdins.29:05 Goal scored
Goal! - Michael Bostwick - Peterboro 1 - 0 Derby Michael Bostwick fires in a goal from just inside the area to the top right corner of the goal. Peterborough 1-0 Derby.28:33
Corner taken left-footed by Grant McCann from the right by-line, Shaun Brisley takes a shot. John Brayford manages to make a clearance.27:52
Conor Sammon challenges Grant McCann unfairly and gives away a free kick. Shaun Brisley restarts play with the free kick.26:52
Shot from just outside the box by Saido Berahino misses to the right of the target.24:38
George Boyd gives away a free kick for an unfair challenge on Gareth Roberts. Direct free kick taken by Gareth Roberts.23:46
Michael Jacobs sends in a cross, Nathaniel Knight-Percival manages to make a clearance.23:19
Michael Jacobs takes the inswinging corner, clearance made by Shaun Brisley.22:51
George Boyd challenges Jeff Hendrick unfairly and gives away a free kick. Direct free kick taken by Paul Coutts.22:13
Paul Coutts produces a cross, Mark Little manages to make a clearance.21:39
George Boyd takes a shot. Blocked by Will Hughes.20:21
The ball is swung over by Conor Sammon, clearance made by Shaun Brisley.20:02
Centre by Grant McCann, clearance by Michael Jacobs.18:19
Long range effort from Theo Robinson misses to the left of the target.16:55
John Brayford delivers the ball, Shaun Brisley manages to make a clearance.16:24
Jake Buxton fouled by Saido Berahino, the ref awards a free kick. Direct free kick taken by Jake Buxton.14:49
Michael Jacobs takes the inswinging corner, save by Robert Olejnik.13:55
The assistant referee flags for offside against Theo Robinson. Indirect free kick taken by Robert Olejnik.13:03
The assistant referee flags for offside against Theo Robinson. Free kick taken by Robert Olejnik.11:56
Craig Alcock gives away a free kick for an unfair challenge on Theo Robinson. Michael Jacobs crosses the ball in from the free kick, clearance by Grant McCann.9:24
John Brayford sends in a cross, save made by Robert Olejnik.9:06
The ball is swung over by Theo Robinson, Kgosi Ntlhe makes a clearance.8:36
Michael Bostwick takes a shot. Blocked by Will Hughes.6:26
Corner taken by Paul Coutts.3:34
Corner taken right-footed by Paul Coutts, Richard Keogh has a headed effort at goal from deep inside the area missing to the left of the target.1:38
Mark Little fouled by Will Hughes, the ref awards a free kick. Free kick crossed by Grant McCann, Shaun Brisley challenges Gareth Roberts unfairly and gives away a free kick. Free kick taken by Adam Legzdins.0:00
The game gets underway.
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