Gyan knows very well the qualities Sessegnon can bring to the Black Cats' table and feels his time in England will be a success.
"He's a fantastic player. I know him from France and he was one of the best players in France," Gyan said.
"He hasn't played for quite a while, but since he came here, he has done well in the Premier League. He's a ball juggler and if he is in top shape, he will help the team."
And Sunderland manager Steve Bruce agrees with Gyan's thoughts despite a tough start to his Premier League life.
"The kid is disappointed because he has come in and played really, really well in a couple of games and we haven't won a match yet," Bruce said.
"But you can see he has taken to it straight away. I think he will be a big crowd-pleaser - he's a good player, the kid, and hopefully there's a lot more to come from him."