The midfielder has been linked with Wolves ahead of the winter market and was dropped for defeat to Juventus.
But Massara says, "We are talking about a technical decision.
“The coach saw that Kessie was going through a difficult period.
“This week he wasn't able to train at his full capacity and he also had some minor physical issues.
“(Stefano) Pioli decided to not go with him for this match, but we are convinced that Franck will be able to get back to being the player we all know very soon."