Manchester United and Arsenal are again at the centre of controversy in the wake of their match at Old Trafford.
Last season Arsenal's players vented their fury towards Ruud van Nistelrooy after he missed a last-minute penalty.
This time around the referee Mike Riley is the target of Arsenal's anger as they feel they were on the wrong end of the major decisions during the game.
BBC Sport analyses whether the Gunners' complaints are justified.
FERDINAND'S CHALLENGE ON LJUNGBERG
Freddie Ljungberg was played through on goal by a defence-splitting pass from Edu and got to the ball before United central defender Rio Ferdinand.
Ferdinand was the last defender and, as he ran across into Ljungberg's path, he only succeeded in clumsily bringing down the Arsenal midfielder 35 yards out.
Arsenal will argue this was a professional foul if the letter of the law is applied as the Swede would have been clean through on keeper Roy Carroll's goal.
But to Arsenal's dismay Ferdinand did not even get booked as play was waved on and his only saving could have been that Ljungberg's first touch was too heavy and he would not have got to the ball.
VAN NISTELROOY TACKLES COLE
There is little doubt this was an ugly challenge by Ruud van Nistelrooy on Ashley Cole and makes you wince every time you see it.
Cole is trying to shield the ball under pressure from the Dutch striker who is clearly seen on television replays dangerously running his studs down the side of the Arsenal defender's leg from the knee down.
Again, the United player escaped without punishment even though the incident occurs close to the touchline being patrolled by the non-flagging assistant referee.
Arsenal boss Arsene Wenger wants the tackle reviewed by the Football Association and appears to have a strong case.
ROONEY PENALTY DECISION
Campbell is not happy with Rooney's fall to ground
A huge decision and the turning point of the game. Rooney turns into the Arsenal box and runs at Sol Campbell.
He jinks to the right leaving Campbell slightly wrong-footed and the central defender throws out his left leg to try and get a touch to the ball.
Rooney goes down over Campbell's trailing leg and wins a penalty, although the Arsenal player screams at the teenager while he is on the floor and accuses him of diving.
But referee Riley has pointed to the spot to the disbelief of Campbell in what appears to be a good decision to most at first glance.
However, television replays show that contact was minimal and the referee was fooled into awarding a penalty.
The referee only gets one look and this is not the first or last time an incident like this will happen as it is part of the game.
Arsenal should turn their minds back to the penalty Robert Pires won against Portsmouth last season.
COLE CLASHES WITH RONALDO
Arsenal are chasing the game and consequently leaving themselves short at the back.
United winger Cristiano Ronaldo tries to take advantage on the counter attack and goes down under a sliding Cole tackle in the corner of the box.
This time Riley waves away any penalty appeals despite this appearing to be a more legitimate shout as contact was made.
Arguably, if Arsenal were not behind, they would still have
been more organised and disciplined in defence and the opportunity might not have arisen.