The club captain has found himself frozen out in recent weeks.
Wenger said: "Thomas is one of the best defenders in England, like the two others.
"I told them at the start of the season that we have three outstanding central defenders.
"It's about game by game that I make a decision - and it is about partnership as well.
"Thomas has been a substitute for quite a few games and he still plays a big part in the game - I don't see him as a substitute at all."