Quinn said: "Was it a big decision? It was and it wasn't.
"Quite honestly, 12 or 18 months ago I was telling Peter Reid that I couldn't go on but he convinced me I could and now time has finally run out for me.
"I wanted to do things properly because there might have been confusion that when Howard Wilkinson took over I didn't want to stay at the club and that was not the case.
"But maybe the change of manager made me realise that a whole new thing was happening at the club and I couldn't really help him any more as a player."
A Sunderland player for the last six years, Quinn will now take an ambassador's role at the club.
Quinn began his career at Arsenal in 1983, spending seven years at Highbury before moving to Manchester City in 1990.
The striker's last appearance for Sunderland was in the 1-0 home defeat by West Ham United on 19th October.
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