The 36-year-old former Ghana captain spent more than a decade in Italy, playing for Udinese, Parma, Brescia, Bologna, Cesena and Juve.
"Gennaro Gattuso was my most difficult opponent during my time as a footballer," Appiah told Starr FM.
"I first faced him when I was playing for Udinese and Gattuso was playing for Salernitana and he was too strong.
"I wanted to show him my African body and he was too strong even at that time,” he added.
Appiah boosts of 67 caps for Ghana, scoring 16 goals in the process.
He was part of the Black Stars squad in their maiden participation at the Fifa World Cup in 2006 and played in five Africa Cup of Nations tournaments.