Pierre-Emerick Aubameyang was sent off against Crystal Palace for the first time in his Arsenal career
Coach Mikel Arteta said it is a "big shame" Arsenal will be without captain Pierre-Emerick Aubameyang for three games after his ban was upheld.
The Gabon striker, 30, was booked for a tackle on Max Meyer in the 1-1 draw at Crystal Palace but the video assistant referee overturned the decision.
Arsenal appealed against Aubameyang's red card but his suspension will stand.
"It's a big shame and a big loss for us, but he mistimed the tackle and we have to accept it," said Arteta.
"It's an action that is completely accidental, in my opinion. He's been superb under me, he's working so hard. He's scoring goals and has probably been the most important player so to lose him is really bad news for us.
"Players have to step up. You know, when one of your big players is not there, they have to take responsibility."
Aubameyang will miss Saturday's home match against Sheffield United and Arsenal's trip to Chelsea, as well as their FA Cup fourth-round tie at Bournemouth.
He is the Gunners' top scorer, claiming three goals in four Premier League games under Arteta to reach 14 for the season, while fellow striker Alexandre Lacazette has failed to score in six games.
"You can help him by talking to him and giving him confidence, but that ball has to end up in the net," Arteta added. "I think that's the best medicine for strikers.
"What we have to try to do is put 'Laca' in positions where he can have as many opportunities to do that as possible during a game."
Gunners short in defence?
Arsenal have been linked with Manchester City defender John Stones and AC Milan midfielder Franck Kessie but Arteta denied they have any interest.
"John is a player that I really like and I followed," said the former City assistant coach. "We signed him when I was at Manchester City and I worked with him for many years and know him well.
"When I look at centre-backs he has many attributes that I like from one, but we're not interested."
Arteta revealed that Sead Kolasinac could miss Saturday's game with a thigh strain while fellow defender Calum Chambers is a long-term absentee having undergone surgery on a ruptured ACL.
"We have a lot of issues at the back," said the Gunners' boss. "The fact that Calum got the big injury is modifying our plans. We have to live with it, this is what we have.
"I'm happy we have the squad that I believe we can compete for what we want, but if this scenario changes and we need somebody, I'm expecting that we will go into the market and try to solve the issue."
-- Courtesy of BBC Sport