O'Neill said: "Everyone will come in for criticism at certain stages. I'm not going to go down the route of singling out any players.
"Everyone has a responsibility, every time you step on the pitch. In every Premier League game you play, you have a chance of doing well or playing poorly.
"Overall I've been very pleased with Zat. He got into the side a week or 10 days before Curtis Davies arrived here and I've been impressed. I've been pleased with the efforts of a lot of the team."