Australian teenager Nick Kyrgios defeated Santiago Giraldo 7-6 (7/3), 7-5 on Tuesday at the ATP Toronto Masters to set up a second-round meeting with Andy Murray.
The Wednesday showdown will be a huge test for former Wimbledon winner Murray, whose game has gone off the boil this season as he tries to regain his top form after back surgery ten months ago.
The tenth-ranked Scot has not played since he saw his hopes of defending his Wimbledon title dashed in a quarter-final defeat to Bulgarian Grigor Dimitrov.
Kyrgios backed up his growing big-match reputation with his 94-minute win over Giraldo coming after the 19-year-old Aussie knocked Spaniard Rafael Nadal out in the fourth round of Wimbledon.
Kyrgios is making his Masters 1000 career debut this week after rising more than 100 ranking places in the past month and a half.
The number 72 is the only teenager ranked inside the top 100. He equalled his season record at the ATP level to 6-6 with the victory.
Kyrgios played fearless tennis as he trailed the more experienced Giraldo 5-2 in the opening set, with the wild card winning the opener in a tiebreak. He claimed victory on his third match point in the second set after breaking the South American in the final game.
"First match back so I knew it was going to be tough," said Kyrgios. "I came out a bit flat.
"I thought I hung in well. I played the big points pretty well, I`m relatively happy."
Kyrgios said that taking on Murray will be another huge challenge.
"He`s a great player, and I`m just going to go out there and just enjoy the experience to get to play another player like that.
"I`ll hopefully serve well and keep it on my racquet and do the best I can out there. I definitely go into the match feeling like I`ve got a chance and I`m going to get some opportunities.
"But it`s going to be one of the toughest matches I have ever played, so I have just got to be ready for it."
Day two play began three hours late due to rain.
Latvian 11th seed Ernests Gulbis began his US Open tune-up campaign with a defeat of Portugal`s Joao Sousa 6-3, 6-4 while Italian Andreas Seppi beat Canadian Brayden Schnur 6-3, 6-3.