The words from Coates may come as a surprise to Mark Hughes, who replaced Tony Pulis as Stoke manager earlier this week.
Coates said: "We've had seven years with Tony which is quite a long time in modern football. The game is changing and there is a tendency for managers to be at clubs for shorter periods.
"There will be no more Alex Ferguson and even David Moyes with his long period at Everton. But, I believe that you have to give managers a chance. It's a tough job but they get well paid. That goes with the job."
Hughes accepted the job at Stoke City six months after being sacked by Queens Park Rangers.