In the game I saw, which was a domestic game, he was slow to track back, and while the ball was pinging around in his own box, all his team mates were throwing their bodies around to block shots while he was casually standing at the top of the box doing nothing but watching!He was a better defender at Lyon than alot of people give him credit for but he's clearly improved in that area. He wasn't fit and settled last season and dealt with niggling injuries. He was also only 20/21/22 years old at Lyon so still clearly developing.
The stuff he's great at is the stuff you can't teach.