Yennaris was able to play with the Belgian defender in their Carling Cup win over Bolton Wanderers.
"Thomas is just unbelievable, you can see he's a winner," he told Arsenal Player. "He's a great presence to have in the team and a true leader on and off the pitch.
"Everybody knows how good he is so when he's back it's a big boost to the manager. He's a top-class player. When we're called up to train with the first team we are involved with the likes of him and he trains how he plays."