I watched a fair bit of Sunderland this season. It's as if they played a 3+1 instead of a back 4. Yelling was often the odd man out not connected to the other 3. Drifing inside and leaving his wide area responsibility vacant. I doubt that was the strategy.
He was very good 1 v 1, and showed excellent recovering ability, but it was a rare thing for him to venture forward like he did in Brazil. It's almost as if they told him, look don't worry about getting forward, keep you man in front and stay close to the teammate next to you. They treated him like the inexperienced player he is.
He's a lot better than he was in 2015, but still needs work on his entire game except just being fast.