Arsenal head coach Unai Emery revealed he spoke to Alexandre Lacazette about controlling his temperament after the striker was sent off during a surprise Europa League defeat to BATE Borisov.
Lacazette missed a glorious opportunity to open the scoring in the first half and saw an equaliser to Stanislav Dragun's header ruled out for offside as the Gunners lost 1-0 in Belarus.
He was then dismissed with five minutes remaining for swinging an elbow towards Aleksandar Filipovic as they tussled for the ball.
After the game, Emery admitted he had already had words with Lacazette about the issue – with the Frenchman now banned for the return leg at the Emirates Stadium next Thursday.
"I didn't see the action but we spoke and frustration needs controlling," he said.
"It's bad news with the red card. Next week we aren't going to play with him but now we are going to think with the players that are okay for next week."
Lacazette later posted an apology on Twitter, backing his team-mates to overcome the deficit without him.
"Letting the team down like that is the worst feeling," he wrote.
"I should have stayed calm but it's not always easy.. Sorry. There are still 90 minutes to play and I believe that my teammates will make it to the next round."
Emery, who named a strong side at the Borisov Arena, making just two alterations to the team that beat Huddersfield in the Premier League at the weekend, echoed the views of his striker and said he has faith in his squad to turn things around.
"I trust in our players and I trust in our stadium and supporters," he said.
"There are two matches. Tonight's match is important but we can't (be knocked out), we are going to play a second match next week.
"I trust in our work to prepare for the next match and to have a different result in Emirates Stadium.
"It's a difficult match. Next week we are going to play another 90 minutes and I am sure it is going to be different.
"Today the first half was a good performance for us, we had chances to score, sometimes last week our chances were a goal and today is not. We worked. I am happy with the players as we worked and we tried."
The defeat was made all the more galling by the fact BATE, the reigning Belarusian Premier League champions, have not played a competitive game since mid-December.
Despite winning 13 consecutive league titles, the club have struggled in Europe and this is only the third time they have made it to the Europa League knockout stages.