Arsene Wenger needs to instil greater discipline into his players after three of them were sent off within a week, former Arsenal manager George Graham said on Sunday.
French striker Olivier Giroud was dismissed in the Champions League defeat by Dinamo Zagreb on Wednesday and Gabriel and Santi Cazorla both received red cards during a feisty London derby at Chelsea on Saturday, which the home side won 2-0.
Wenger was furious that Chelsea's Diego Costa escaped with only a yellow card after becoming involving in several incidents and apparently provoking Gabriel.
In the Wenger's 19 years at the club, they have had more than 100 sendings-off and Graham, who managed Arsenal from 1986-95, said the Frenchman had to take some of the responsibility.
"He is not the most strict manager and he really needs to get hold of his own players because there's no way (Gabriel) should have been sent off," Graham told the BBC's Sportsweek programme.
"It's (Gabriel's) own stupidity that got him sent off and they've got to handle that."
Graham agreed that Costa should also have been dismissed and predicted that referees would be stricter with him after Saturday's incidents.
"He is going to be targeted now by the officials and probably rightly so," he added.
"Although you've got to keep that physical intensity, once you step over the mark he's got to be dealt with by officials, it's as simple as that. And I think he will be."