Mannone predicted after the 1-0 defeat at Hull last month - when Sunderland were reduced to nine men - that their second-half shut-out could prove a turning point.
Ahead of successive home games against Chelsea tomorrow and Tottenham on Saturday, the Italian said: "I thought everything changed when we kept a clean sheet after the sendings-off.
"That was massive in our mentality and now we look much more solid.
"We've stopped giving away cheap goals and you can't believe how much confidence it gives you when you feel solid."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball