The Portuguese was unhappy with the Englishman's performance in the 3-0 win over Pacos De Ferreira on Thursday, which sealed their place in the Europa Conference League group stage.
However, Nuno believes that Sessegnon, who spent last season at Hoffenheim, has plenty of potential to get better.
He said; "I will start with Sessegnon. I think he is struggling, he is struggling.
"A lot of time out of competition. He has talent. He is a player that can give us good things, one vs ones, crossing, he has energy but he did not do all that he has today.
"I truly believe that he has much more that he can give."
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!