Violetta Degtiareva, who was commonly referred to as the “next Anna Kournikova,” died suddenly during a training session Wednesday. She was 23.

Violetta Degtiareva Dies

Degtiareva was in the midst of training when she dropped dead of heart failure, reported the New York Post. Further details of her passing have yet to be revealed.

Anastasia Vdoveno, a fellow tennis player and close friend of Degtiareva, took to Facebook upon her sudden death, writing, “I can hardly believe it. Rest in peace.”

During her tennis career, the Russian tennis player’s highest ranking was 947 in the world.

Though she never won a major title, she did reach the quarter-finals of the ITF-Turnier pro circuit tournament in Turkey and was one of the highest-earning stars on the International Tennis Federation pro circuit.