Ogbonna was speaking after their victory over Aston Villa last night.
"The potential of the squad here has always been high, always," centre-back Ogbonna told the London Evening Standard.
"I want to give a big credit to the manager. Since he came in, he changed a lot of things: discipline, hard work and you can see on the pitch. He has a lot of credit on that one.
"Has he given us belief? Of course, of course. We want to achieve what we achieve in the future, I don't know what [we can do] but if we perform we can get good results. Sometimes we can be lucky, sometimes not. I think if you change your mentality something positive can happen."