If you watch the replay from behind the kicker you don't even see the man who starts out standing beside Sami, so I think it's a bit misleading. Finnan is ball watching while Luisao makes an untracked run behind him. I also think that not enough credit has been given for the delivery. Our defenders were poorly positioned to defend such a delivery given that none of them were marking the zone where the goal was actually scored from. However, it's Finnan who was best placed to pick up Luisao. While the ball is in flight both Luisao and the other guy are making runs....Sami can't be expected to pick up both and given that the freekick has caught our defence out Finnan should be picking up runners instead of watching the ball go over his head? Also with a zonal system this statement surely doesn't apply? "you're not seriously suggesting that Finnan, who isn't the best header of the ball, was supposed to mark their best header of the ball?" Sami was presumably detailed to mark the most dangerous zone, not the most dangerous header of the ball.