Felix’s recent form has been questioned in Spain even as he has been the subject of speculation in Britain that Manchester City want the 21-year-old Portuguese to replace former Atletico striker Sergio Aguero.
“Joao is a very important player, he started the season at a very high level, we need that player,” said Simeone. “All footballers go through different phases in their careers, especially when they are young.”
With Felix alongside him at the press conference, Simeone dismissed doubts about the striker’s defensive work-rate.
“We all want him to grow and for him to grow and get to where he wants to be, he has to be complete and have different facets, because all footballers want to work for the team.”
Felix echoed his coach.
“I’m happy at the club,” he said. “Like all players I have not so good phases, I don’t know if I’m going through one or not, but I’m sure it will pass.”
“I don’t want to be one of them, so I try to apply my desire and my talent.”
Chelsea are unbeaten since Thomas Tuchel took over from the sacked Frank Lampard in late January.
“We are facing a team that is doing very well, that has not lost since the arrival of its new coach,” said Simeone.
“But tomorrow, we will be looking for one result: victory. And we’ll try to play the game the way we need to achieve that objective.”