The winger has announced he intends to leave the Potters at the end of this season.
"He has been an excellent player for this football club and a good person too," Coates told The Sentinel.
"At his best, he made a very great impact for the team, and one of our best periods came when he was at his best."
Etherington arrived at Stoke with reported debts of around £1.5m and he later admitted to lapsing again, but he has since banished his demons and reformed his personal life.
Coates added: "He had his problems when he came, but he has now resolved them and is settled with his family. We were really pleased to help him at the time, and it gives us a lot of pleasure when it works out well for the individual."
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