Andrey Rublev defeats Dominic Thiem in Melbourne Opener
Rublev awaits either Emil Ruusuvuori or Australian qualfiier Max Purcell in the second round.
Elsewhere, Borna Coric thrashed Mikhail Youzhny to set up a second-round tie with Rafael Nadal.
Argentina's Diego Schwartzman saved four match points to shock third-seeded Dominic Thiem 6-4, 6-7 (7/9), 7-5 in the second round of the ATP Montreal Masters.
World No.36 Schwartzman seized the initiative against the seventh-ranked Austrian, who fell at the first hurdle after enjoying a first-round bye on Tuesday
On the defensive early, Thiem held on to level the match at a set apiece on his fifth set point of the second-set tiebreaker.
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And the 23-year-old appeared to have gained control when he powered to a 5-2 lead in the third set.
But Schwartzman wouldn't go away, saving two match points on his serve at 3-5, another in the next game and yet another as he served to take the set to 5-5.
Schwartzman then broke to serve for the match. He fell behind 0-40, but won the last five points of the match for his first win over a top-10 player and a berth in the third round.
Schwartzman's wasn't the only great escape of the day.
Canadian teenager Denis Shapovalov saved four match points en route to a three-set victory over Rogerio Dutra Silva in their first-round encounter.
The 18-year-old trailed 4-6 in the second-set tiebreaker but saved all four match points he faced to force a third set.
"I don't remember all of them. Honestly, it's a little bit of a blur," Shapovalov said.
"I remember one of them, he passed me. I hit a pretty tough volley. It was a pretty long point there. On one of them, I remember I was pretty far back. I went for a backhand down the line, which was pretty good. I wasn't holding back.
"I just told myself, he's got to win it from me, I'm not going to give it to him. I think I did a good job to stay tough out there."
Shapovalov broke Brazil's Dutra Silva in the seventh game of the third and went on to close out a 4-6, 7-6 (10/8), 6-4 victory.
"It's matches like this I live for and that I play for," said Shapovalov, who earned a second-round meeting with former US Open champion Juan Martin del Potro of Argentina.
With old-guard stars Rafael Nadal and Roger Federer taking a day off — 19-time Grand Slam champion Federer to celebrate his 36th birthday — Shapovalov was one of a wealth of young talents to shine on Tuesday.
South Korean 21-year-old Chung Hyeon withstood 16 aces to beat 2014 semi-finalist Feliciano Lopez 6-1, 4-6, 7-6 (7/3).
After the third set went to the tiebreaker without a break of serve, the 56th-ranked Chung built a 4-2 advantage and went on to secure the victory in two hours and 16 minutes.
He next faces ninth-seeded Belgian David Goffin, a 4-6, 6-1, 6-4 winner over Japan's Yuichi Sugita.
Croatian 20-year-old Borna Coric breezed past Russian lucky loser Mikhail Youzhny 6-2, 6-4 to set up a second-round meeting with top-seeded Nadal.
Coric has won two of three prior encounters with the Spanish great, who won a 10th French Open title this year and can regain the world number one ranking with a run to the semi-finals this week.
American Ernesto Escobedo, 21 years old and ranked 85th in the world, got his chance as a lucky loser when 10th-seeded Czech Tomas Berdych withdrew with a rib injury.
Escobedo stepped in and defeated Georgia's Nikoloz Basilashvili 7-6 (7/4), 6-4.
In other first-round matches American Sam Querrey defeated Vincent Millot for the second time in as many weeks, peppering the French qualifier with 18 aces in a 4-6, 7-6 (7/4), 7-5 win. Querrey beat Millot in the quarter-finals at Los Cabos en route to his 10th ATP title.
American Jack Sock, seeded 15th, also advanced, downing France's Pierre-Hugues Herbert 7-6 (7/4), 6-3
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