No player has made me lose as much hair and mental stability as Nagatomo. He had an impact alright, not sure if it's a positive one.
Edit: Forgot about Kuzmanovic but Nagatomo is a close second.
What how?
So many players have been way worse and way more useless in that era! He never was great but he was not as bad as people make him out to be!
From the top of my head players who were more usless than him in the same era: Poldi, Kuzmanovic, Schelotto, Pereirra, Montoya, Zarate, Osvaldo, Vidic, Mvilla, Santon, J mario, Kondogbia, Rannochia, Belfodil, Johnatan, Obi, Laxalt, dodo, Taider, Poli, Gargano, Ansaldi ..... and i m pretty sure the list still goes on. Also keep in mind that most of these guys cost us a lot more than naga did.
Problem with naga is that he was avarage at best during his whole inter career maybe except for the first year where he was quite good.