Alexander Zverev is destined to win a Grand Slam title but how long that breakthrough takes depends on when he develops a more ruthless streak, according to one of the sport's toughest competitors Mats Wilander.

Alexander Zverev of Germany celebrates after winning the men's singles first round match of the French Open tennis tournament against John Millman of Australia at the Roland Garros in Paris, France on May 28, 2019. (Photo by AFLO)