The former Arsenal striker told the Guardian: "I had a week to sort out my future and it was one of the biggest decisions of my life but, ultimately, it came down to the fact Roy Keane was at Sunderland. I went to Celtic, and also Charlton, and at both clubs they wanted me to sign there and then. They put a lot of unfair pressure on me.
"Celtic, in particular, knew I wanted to play for them but it wasn't fair the way they suddenly produced a contract, put it in front of me and expected me to make up my mind straight away. A few other things went on, but at Sunderland it was totally different. The gaffer's exact words were, 'Take your time, there's no pressure.'"