Denis Shapovalov achieved a significant career milestone on Tuesday after coming from behind to beat Tomas Berdych in the first round of the Italian Open in Rome.
The 19-year-old's 1-6 6-3 7-6 (7/5) win means he is guaranteed to eclipse Milos Raonic and become the Canadian number one when the new rankings are revealed next week.
Shapovalov, fresh from reaching the semi-finals in Madrid last week, endured a nightmare first set but gradually found his range then held his nerve to claim another notable victory.
He told atpworldtour.com: "I'm a little bit in shock. It's definitely happened extremely quickly. I've worked hard to achieve this for a long time in my career, and it's crazy that it's come so early."
On a day interrupted by rain, there were also first-round wins for 14th seed Diego Schwartzmann, who beat Chile's Nicolas Jarry 6-4 6-1, and 16th seed Lucas Pouille, a 6-2 3-6 7-6 (7/3) winner over Andreas Seppi.
Damir Dzumhur brushed aside Spanish veteran Fernando Verdasco 6-3 6-1 while there were also wins for qualifiers Nikoloz Basilashvili and Stefanos Tsitsipas.
In the second round, ninth seed David Goffin beat wild card Marco Cecchinato 5-7 6-2 6-2, and Philipp Kohlschreiber beat American Jack Sock 6-4 6-3.