Ex-Ghana captain Stephen Appiah has served notice to the Black Stars to be wary of Cristiano Ronaldo at the World Cup because he can “single handedly” change a game.

The four-time African champions will be playing USA, Germany and Portugal at the group stages of the World Cup.

The former Juventus and Udinese midfielder conceded that the Real Madrid free scoring striker can be Ghana’s killjoy thus his lethal attacks must be neutralised.

Appiah opined that the current world’s best footballer is peerless at national level and has been the fulcrum of A Seleção, especially during the 2014 World Cup play-offs against Sweden.

“There is a guy [Ronaldo] who has overshadowed all the players but they have a good team and nobody is talking about the other players,” Appiah told Goal Ghana. “He is making the difference anyway and I think you watched the game against Sweden and you saw what he did so that tells it all.”

On Ghana’s opening game against the US, the 33-year-old described the clash as “a revenge” for the Stars and Stripes since the Black Stars have beaten them twice on the same platform.

“It is going to be difficult because beating them on two occasions it is never going to be easy,” Appiah noted. “What I don’t like is if we were going to play them in the second or third game then they would have played Germany or Portugal and lost therefore their morale will be down.”

“But here is the case they are playing us first and that will be difficult and definitely they are coming for revenge.”

On a personal note, Appiah hinted he may return to the field at club level hence he will talk about his testimonial game “when I decide to retire… you’ll see it. Never say never in life.”