Casemiro has dismissed the idea of reversing his decision to leave Manchester United at the end of the season.
The midfielder has been rejuvenated under Michael Carrick, scoring two goals in his last three Premier League matches.
United announced in January that Casemiro would leave the club when his contract expires after four seasons at Old Trafford and more than 150 appearances.
Speaking after playing in Brazil's 2-1 defeat by France in comments reported by The Athletic, the 34-year-old said: "I am still enjoying it a lot [in Manchester].
"It is huge, the affection that the fans have shown towards me. But I do really believe the decision is made and done. I believe it will be some difficult moments, these [final] games at Manchester United."
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Casemiro, who previously spent a decade at Real Madrid, had warm praise for Carrick and the impact the former midfielder has had since taking over from Ruben Amorim on an interim basis.
"Above all, Michael is a specialist in my position on the field, he was a truly great player," he said.
"That makes everything much easier and he is always talking to us. I feel like we are in a good dynamic right now in Manchester and my objective now is to get the club back into the Champions League."
United have won seven of their last 10 games to climb to third place in the Premier League table and will face Leeds United in their next match on April 13.
