Not impressing during a single season at a dysfunctional team like Sunderland should not count much against a player. Not that I know anything about this guy, really.
Generally, this summer's transfer market will be extremely interesting. The World Cup summers always are. You'd think that with modern data analysis and extensive scouting systems a tiny sample of NT games wouldn't change a player's transfer profile too much, but in many cases it definitely will.
Irriducibili? No thanks, I'm a fan of Lazio.