Cattermole told the Sunderland Echo: "John came in during the summer and straight away, all the headlines were 'Lee loses the captaincy'.
"Maybe that put a bit of doubt in my mind. The gaffer made it clear to me that that wasn't going to be the case. But it's stuff that adds up and you start asking questions of yourself.
"I'm a confident lad, though, and I don't think you become a bad player overnight.
"If you look at the amount of games I've played for my age, there won't be many in the country who've played more.
"I've been a regular now for a long time and I'm really hungry. I thought I did well at Man United and had a decent game last weekend.
"It's been hard, but I think it's going to make me a better player.
"You get confidence from playing well at a place like Man United and my level of training has gone up since then."