The Frenchman believes that the 23-year-old, who scored at the Veltins-Arena in their 2-2 draw, was one of the best players against the German club.
"Football performances are in every single game," he is quoted as saying by the BBC. "Theo did extremely well today; he was one of our best players.
"But he has been injured for a long time, injured with England, and comes back now. We know he is a great player."
Arsenal are currently second in Group B with seven points from four matches, one point behind leaders Schalke.