The Welsh lost 30-22 following a passionless display as Italy ended a run of 14 successive defeats to record only their second win in the competition.
But Hansen vowed to spearhead the recovery process before Wales face the immense task of tackling England in Cardiff in a week's time.
"We scored three tries but they were the only times we won the collisions with Italy," said the New Zealander.
"We missed tackles and got the basics wrong. The question will have to be asked whether we had the right attitude. We will have to look at ourselves and learn from this performance.
"I know it is painful for everybody but it is two times as painful for the players. Now they will be judged by their actions."
Hansen, who hauled off skipper Colin Charvis in a desperate second-half act, added: "It was not the start we wanted, it was pretty disappointing. But we have got to give Italy credit and they thoroughly deserved the win.
"It tells us we played very, very poorly. Some days you wake up and have a bad day and we certainly have had one of those.
"We can't dwell on this performance and make it worse than it was and let it drag right through next week and effect the build-up to England."