Vasek Pospisil has stopped working with his coach, Frédéric Fontang, the 26-year-old Canadian said in a statement.
Pospisil started his partnership with the French coach almost four years ago. He frequently credited him for much of his improvement, as he climbed from below the Top 100 into the Top 25 in January 2014.
"I will always be grateful for his work ethic, commitment and passion for the sport, and for his efforts in making me a better tennis player," he said in a statement. "I would like to thank Frédéric for always conducting himself in a professional manner with the utmost integrity; following a clear set of principles and staying true to his values."