The 26-year-old Benin midfielder arrived at the Stadium of Light in a ?6million switch from Paris St Germain in January, and has already impressed during his few weeks on Wearside.
Sessegnon's form, however, has come as no surprise to Gyan, who saw him at close hand during his own spell in France with Rennes.
Super starter: Sessegnon has impressed following his switch from PSG
He said: 'He's a fantastic player. I know him from France and he was one of the best players in France.
'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.'
Sessegnon made his Sunderland debut in the 4-2 home defeat by Chelsea on February 1, and has played every minute of the three games the club has contested since his arrival.
Despite his best efforts, he has finished on the losing side on every occasion, a run which has seen the Black Cats slip out of the top six.
However, manager Steve Bruce has been delighted with his contribution so far and is confident there is more to come.
Spotlight: The onus is on Gyan to score the goals after Darren Bent's move to Aston Villa
He said: '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.
'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.'
Bruce has handed his players a short break with the club having no fixture this weekend, and they will return desperate to end their losing streak despite facing a tough run of fixtures.
They resume at Everton on February 26 and then head for Arsenal and Manchester City either side of Liverpool's visit to the Stadium of Light on March 20.
By that point, Bruce hopes to have Michael Turner and Fraizer Campbell back from injury and Lee Cattermole and Danny Welbeck close to returns.
The presence of John Mensah in the team for the last two games following his recovery from an ankle problem and Sulley Muntari's arrival on loan from Inter Milan have strengthened the manager's hand, and Gyan for one has been delighted to link up once again with his Ghana team-mates.
He said: 'I have played with them for a long time - eight years in the national team.
'I have played will Sulley in a club side at Udinese and I know what he can do, and if he gets the ball, I know what he wants to do.
'It's a good move for him. I have seen Sulley play for a long time and it's a good thing for the team.' Sunderland chief Quinn in quit threat to fans watching illegal games in pubs Bruce blasts Capello after Italian claims Bent is better away from SunderlandHull close in Leicester star Hobbs while Sunderland loan out youngsterAll the latest Sunderland news, features and opinion
Explore more:People: Michael Turner, Steve Bruce, Lee Cattermole, Danny Welbeck Places: Liverpool, France, Ghana