Nottingham Forest earned a valuable three points at Peterborough to take them seven points clear of the relegation zone.
But the gloss was taken off the win when Garath McCleary was shown a straight red card, meaning he will now be unavailable for the next three games.
Forest were superb from the kick-off and completely dominated the first half with 11 shots on target and were unlucky to be going in at half time only a goal up.
It was a more difficult second half for Forest, playing the final 20 minutes with ten men, but they were still the dominant side and thoroughly deserved the win.
A good start by Forest saw them laying siege to the Peterborough goal from the outset.
They had the first chance of the game when Chris Gunter
's cross came to Andy Reid
on the edge of the six-yard box where he headed the ball back across to Dexter Blacskstock who got his head on it to send the ball towards goal, forcing a great save from Paul Jones, diving to his right to tip round the post.Lewis McGugan
didn't take long to mark his return when he dribbled the ball forward and weaved away from two defenders before smashing the ball into the box where it crashed against the inside of the post and back out.
Forest missed a real chance to take the lead when Radi Majewski
's shot was parried away. The rebound evaded Reid and Adlene Guedioura
followed up, but sent the ball over the crossbar from eight yards out.
But they continued to dominate and came close again when the ball was played to Blackstock's feet at the near post and Gabriel Zakuani did well to clear the danger.
They got behind the Peterborough defence again with another great ball by Reid to the on-running Garath McCleary
whose effort was blocked.
After a missed chance by Peterborough, Forest were soon back on the attack when Blackstock laid the ball off beautifully for Majewski, whose left-foot shot from 15 yards could only win Forest their sixth corner of the game.
Peterborough made a rare break with Paul Taylor skipping away from McGugan and Greg Cunningham
and picking out David Ball in the penalty area, but Chambers got back to block and clear.
Forest finally got the goal they deserved seven minutes before the break following a great run by McCleary and a super touch by Blackstock inside the six-yard box, where he turned away from his man and sent the ball off the underside of the crossbar and into the far corner of the net.
After another break by Peterborough there were calls for a penalty from the home crowd when George Boyd went down inside the area, but neither the referee or the linesman were interested.
Forest missed a chance late in the half when Blackstock got away from his man and was clean through on goal where Jones did well to come out quickly and block the effort.
The home side came close to an equalizer just before the half time whistle when Ball got in behind Luke Chambers
who recovered well but the ball went back to Ball and in a mass scramble Chris Gunter
got in with a sliding tackle and Joel Lynch
Lee Camp made his first save of the game early in the second half when Taylor got past Guedioura and smashed the ball towards goal but the Forest keeper managed to dive quickly to palm the ball round for a corner.
Peterborough couldn't prevent McGugan getting away and making a great run down the left before rolling the ball across the six-yard box but a lunging clearance from Tommy Rowe prevented McCleary from getting on the end of it.
Forest threatened again when Joe Newell's header into his own penalty area gifted Majewski a chance and Jones had to scramble to get the ball round the post.
Reid was the first Forest player to be substituted, replaced by George Elokobi in the 64th minute.
Forest were down to ten men when, with 20 minutes to go, McCleary was shown a red card for a lunging challenge on Grant McCann, who made a meal of being brought down after they both went for the ball.
Peterborough looked to get back level when Taylor shot from an angle but Camp got his body behind it to make the save.
With Forest looking to defend their lead former Peterborough defender Scott Wootton came on in place of McGugan and with six minutes remaining a tired-looking Blackstock was replaced by Marcus Tudgay.
A mix-up in the Forest defence gifted Peterborough a late chance but when the ball fell to Boyd he completely mis-kicked and Camp was easily able to gather it up.
It was a tense four minutes of stoppage time but Forest kept their nerve to secure the win.
Nottingham Forest:Camp, Gunter, Chambers(C), Lynch, Cunningham, McCleary, Guedioura, McGugan(Wootton 73min), Reid(Elokobi 64min), Majewski, Blackstock(Tudgay 84min)
Subs not used: Smith(GK), Higginbotham,
Bookings: McCleary 70min RED CARD
Scorer: Blackstock 39min
Peterborough United: Jones, Zakuani, Boyd, McCann(C), Sinclair(Ball 17min), Rowe, Newell(Tomlin 61min), Brisley, Frecklington( Kearns 56min), Taylor, Alcock
Subs not used: Lewis(GK), Little,
Booking: Rowe 84min
Referee: Carl Boyeson