O'Neill admits Cattermole must carry on working hard to ensure he does not pick up so many yellow cards and suspensions, but his performances on the pitch have impressed the Black Cats boss.
"Cattermole has been excellent since I came to the football club - and he may well have been before, I don't know about that," O'Neill told the Sunderland Echo.
"He's 24 and he's the captain of the side. Sometimes he needs to keep his discipline better because over the course of the year I expect he'll pick up a couple of silly bookings.
"I don't want to build him up too much though - particularly as he has a contract to sign here!"