They support the notion that we don't defend the flanks great. Southampton don't really have 10's that are going to cut you open through the centre, they have Boufal and Redmond who are wide attacking players. I watched Sissoko stand off way too much and allow players to jink right and cross, and him and Eriksen just weren't diligent enough.
I don't know why he didn't take Eriksen off when he put Dier on and shuffle Winks out right of the CM4.
But this isn't a unique issue, Sissoko, contrary to mythology, does not protect his RB well when playing RM, especially in the CM2, he doesn't read the game and he ambles about. Go and read what Five wrote in the ratings thread for the Leicester game.