Can he reach those heights again?
He is about to find out - but ask him and he admits he has no idea.
''I really don't know. I can't tell you. I would love to answer that question. I'll just have to put my head down and work hard on my game,'' he said.
''One thing that is great about golf is there is no limitation to age, really. The longevity of the sport is fantastic.''
Campbell, who turned 49 last week, is in Queenstown this week for the New Zealand Open as he eyes a career next year on the seniors tour in Europe and the United States.
The 2005 US Open winner was going to play in the national tournament but an ankle injury has ruled him out.
He retired four years ago but, with the lure of the seniors tours in front of him, he is aiming to play a few tournaments on the European Tour this year.
''I miss playing and competing. That is one thing I have missed over the past four years. I have really enjoyed re-introducing myself to my two boys, Thomas and Jordan, and being an at-home dad.
''I have been cooking for them, taking them to school, watching sport, just being normal. Now it is time to focus on my career, and a second chance at my career.''
Campbell said all his friends around his age, such as Phil Mickelson, Jim Fruyk and Ernie Els, were still doing well.
''I've still got the opportunity to do well. I am nervous and excited at the same time. I just go out and play. Go out with a couple of friends and go out and have some fun.''
Campbell, who won the New Zealand Open in 2000, said he was looking at playing at about 10 tournaments this year. He has a lifetime membership of the European Tour.
He has torn a tendon in his left ankle and, although he can walk fine, it hurts when he swings a club.
The final option is to have an operation but he is working hard on fixing it through physiotherapy. He hopes to be back inside a couple of months.
Campbell, who raced a car around Highlands Motorsport Park with other sport stars yesterday, runs two golf academies in southern Spain and gets back to New Zealand once or twice a year.
The academies are fun but that competitive thrill of playing has not gone away.
''That is the one thing I have missed over the years. Just the ability to compete against the best players in the world.''
He admits he does not linger on his 2005 US Open win.
''It sits on my mantelpiece quite proudly but I don't think about it. It might flash in my mind a couple of times when people mention it. But it is 13 years ago. It is a long time. Of course, wonderful memories and something I will never forget. To be mentioned in the same sentences as those other great golfers is a great feeling.''
