This is, simply put, dire "marking" from Maggio on the second goal scored by Sassuolo on Sunday. He's starting way too central, then only takes one half-glance over his shoulder to see where Sansone is -- and doesn't really react to Sansone's far-post run. There's no near-post pressure that he has to worry about, because Raul Albiol is right there and no other Sassuolo attackers are within 20 yards when they enter the box.
It gets worse when, once the two actually get kind of close, Maggio doesn't bother to check again and actually moves away from Sansone, clearing the way for the Sassuolo attacker to sidestep to the far post for that cross.
We're just going to ignore Maggio getting in Reina's way as he tried to come across to cover the shot, because GOD WHY.