Roma beat Chievo 1-0 on Thursday night to rack up a 10th consecutive win from the campaign's beginning, a feat never achieved before in the Italian top flight.
The capital club are already five points clear at the top of the table, with Napoli and champions Juventus trailing in their wake.
Castan joined the club in 2012, made 30 appearances last season and has played in every game so far this season.
As well as winning their first 10 games Castan and his fellow defenders have only conceded once – the best record in Europe's major leagues.
"We are living through a fine spell thanks to him," he said. "He works a lot and works well, he takes care of a lot of details.
"Not even in Brazil had I managed to win 10 games in a row. We are in a great moment and that is mainly down to him."
Roma travel to face Torino on Sunday, a side they have not lost to since 2007.
