cape Town - Arsène Wenger admits that Calum Chambers' red card at Stoke City killed Arsenal's hopes of completing a comeback.
The Gunners trailed 3-0 at half-time at the Britannia Stadium but hit back through Santi Cazorla and Aaron Ramsey before Chambers received a second yellow card with 11 minutes remaining.
"If you’re 3-2 up then you can’t get a better decision than one of the other team’s players getting sent off," Wenger told the Arsenal Player.
"It was a killer.
"Calum is an easy target because he’s not a dirty player at all. The second yellow card - compared to what happened on the pitch - was a bit farcical.
"He’s only 19 years old and he has to learn [about positioning]. We were a bit young on Saturday at the back and defending is a job for older people. Koscielny couldn’t play and then you have to play defenders who are used to the defending positions."
Alongside Chambers was Per Mertesacker, who played in a slightly unfamiliar role on the left of the centre-back pairing.
"I still think he had a decent game," said Wenger.
"It’s difficult to talk about individuals but as a unit at the back, we were not dominant enough in the first half.
"In the second half I didn’t see Stoke. You come out of the game and you think it’s unbelievable that you come home with nothing out of the game because we didn’t start well."