A crisp injury-time finish that wrapped up a 2-0 win at Bolton Wanderers showed he can sometimes he as good as he thinks he is.
"He can cause you a headache at times, but that's Nick," said the Sunderland manager. "People forget he's only 23, but I can tell you, he's certainly brightened up our dressing room at just the right time.
"He had a bad car crash 18 months ago and he suffers like everybody else. Not just with the car crash but with also not playing regularly. I don't care how good you are and what team you play for, if you don't play week-in and week-out, it becomes very, very difficult.
"I think that Nick with the great Arsenal squad found it difficult because, let's be fair, they play one up the top which is (Robin) Van Persie and Nick seems not to get that opportunity to go where he wants to play.
"I've had a conversation with him, over a cup of tea, and told him he's got to set himself a target. He's a very good finisher with both feet and his head, and he has done really well for us. There's no reason why he can't get you 15 goals a year. That's enough these days. You rarely get players hitting 25 or 30 goals a season anymore.