The Kumasi-giants needed a late volley by midfielder Baba Mahama to see off Proud United in the round of 32 and will hope to qualify to the quarterfinals stage for the third time running.
They are without a defeat after the appointment of Steve Polack as the new manager but the defender believes the visitors can cause trouble.
“We have been preparing very well for the game against Wassaman United. It is not going to be an easy game for us so we have to be fully aware of their threat,” said Frimpong.
“I have belief and confidence in my teammates and I know that we will be victorious on the day no matter how difficult the game will be. Any club that play against Kotoko play above themselves especially when they travel to Kumasi since the players want to impress both the technical team and supporters for future opportunities,” he added.
Although, Frimpong anticipates a tough test, his manager Polack has revealed that he will field several fringe players in the game.
"There's no game on our calendar which is irrelevant since the club has a lot of ambition to achieve. However, I am planning to give opportunities to some of the players who have not been playing regularly since I took over to also have playing time," Polack said.
"They are quality players and deserve some action. They can achieve the target on Sunday so supporters should expect changes in our lineup," he added.