Arsenal manager Mikel Arteta said he was "amazed" to see Declan Rice sent off in his side's 1-1 draw against Brighton after "inconsistency" from referee Chris Kavanagh.
Having already been booked for an earlier foul on Brighton's Joel Veltman, England midfielder Rice received a second yellow card four minutes into the second half for kicking the ball away as the Dutch defender tried to take a free-kick.
Nine minutes later Joao Pedro equalised a Kai Havertz opener to continue Brighton's unbeaten start to the season and end Arsenal's 100% record.
"I was amazed," said Arteta. "Amazed, amazed, amazed because of how inconsistent decisions can be. In the first half, there are two incidents and nothing happens.
"Then, in a non-critical area, the ball hits Declan [on the back of his leg], he turns around, he doesn't see the player coming and he touches the ball.
"By law, he can make that call, but then by law he needs to make the next call, which is a red card so we play 10vs10. This is what amazed me. At this level it's amazing."
The match swung in Brighton's favour after Arsenal went down to 10 men and the Seagulls had 19 shots to three and an expected goal statistic of 1.9.
Arteta believed his side "deserved to win the game" and that Brighton forward Pedro should have been booked for a kicking the ball away once the whistle went in the first half.
But visiting boss Fabian Hurzeler said you cannot compare the incidents and Rice deserved to be sent off.
"For me, clear red card," he added. "He shoots the ball away, it's wasting time.
"You can't compare the two situations. The first with Joao it is clear it is a free-kick and a static situation. The other one is much more like a dynamic situation.
"Please never compare these situations, because in football two situations never are the same so we can't compare these situations."
Rice, booked in the first half for a foul on Veltman, was penalised for a challenge on the same player deep inside the Brighton half near the touchline.
As Veltman returned to his feet, the Albion defender went to take the free-kick quickly and drill it forward but, as he attempted to do so, Rice nudged the ball away.
Veltman continued with his follow-through, kicking the Gunners player in the process and sending him to the ground.
As both sets of players surrounded the referee, Arsenal fans inside Emirates Stadium were calling for Veltman to be shown a card - and there were gasps when it was actually Rice who was sent off. The England midfielder looked stunned.
The Premier League confirmed that Rice was sent off for "delaying the restart of play" - and, according to law 12 on the Football Association's website, this is a cautionable offence.
This includes "kicking or carrying the ball away, or provoking a confrontation by deliberately touching the ball after the referee has stopped play".
Former referee Mike Dean said it was made clear to teams before the season started that kicking the ball away would result in a booking.
"Unfortunately for Declan he kicked the ball away," Dean said on Sky Sports.
"He hasn't kicked it far, but they were told before the season, kick the ball away, delay any kind of restart and you will be cautioned. He was already on a yellow card and he had no choice but to send him off.
"He stopped the restart because Brighton wanted to get it down the pitch quickly."
But former Arsenal defender Martin Keown felt it was the wrong decision.
"I know that Declan knocks the ball away, but why is Veltman knocking the ball into Rice's path?" he said on TNT Sports.
"Where is he [Rice] supposed to go? It is almost like a free punch, 'I'll do somebody at the same time'.
"I know the principle of this new rule, but the referee has a responsibility to keep both sets of 11 players on the pitch – I don't feel it is a sending-off offence."
Ex-Liverpool full-back Stephen Warnock felt Rice needlessly forced the referee into making a decision.
"Declan Rice knows what he's doing," Warnock said on BBC Final Score.
"He has had a little look and pushed the ball away, then the challenge comes in.
"You're asking a referee to make decision in that decision. When you're stood over the ball in that position why do it?"