The Argentina midfielder is weighing up his future with Atletico.
But Simeone said on Friday: "The numbers speak for themselves; he is an important player in midfield and within the team. He is a point of reference and this year has been his best since he joined us.
"Future? He still has one year left on his contract. We will talk about it with the club and then they will decide what is best for both of them."
Positive campaign
Atletico end the season facing Girona and Simeone added: "My assessment is positive. We competed very well, reaching the semi-finals of the Cup.
"We played one of the best games in the Champions League, one of the best we have ever played in, and we already know how it ended. In La Liga we had aspirations until March.
"I had the feeling that this season was the one in which we came closest to competing for the league. We are still frustrated at not having won any titles, which is what the fans love, and I am happy that the fans are demanding that we win a title because that is the way to grow as a club."