Having reviewed the incident Wenger insisted there was no malice in the challenge, but admits the 24-year-old needs to work on his tackling technique.
"I've watched it again and it was not a dangerous tackle, it was a clumsy tackle. But you have to accept you can be punished and he has to learn from that," Wenger told a media conference on Thursday.
"I don't think he wanted to injure anybody. Unfortunately we will lose him for four games at an important stage of the season.
"I think he's not naturally a great tackler, [but] in his decision-making I think he's quite intelligent on the pitch. He doesn't master the technique of tackling.
"I would encourage him not to tackle, to stay on his feet. Tackling you learn at a young age, you can improve it, but when face to face with somebody it's better that you stay up."
Xhaka was previously sent off during Arsenal's 3-2 Premier League win over Swansea City in October.