Pospisil had eight aces against six for Auger-Aliassime, and although he was accurate on just 51% of his first serves, he won 83% of those points.
WATCH | Pospisil at the head of Auger-Aliassime in Vienna:
He beat Auger-Aliassime three times, including the two winning breaks, and saved two of the three break points he faced.
Auger-Aliassime was precise on 74% of his first serves, winning 70% of those points. But he only won 42% of second serve points, compared to Pospisil’s 53%.
Pospisil, ranked 81st in the world, will then face fourth seed Daniil Medvedev. Pospisil is 1-1 against the Russian, winning the last meeting in February at an indoor tournament in Rotterdam, the Netherlands.
Djokovic gets closer to the n ° 1 ranking at the end of the year
Also on Wednesday, Novak Djokovic saved four set points in a 7-6 (11), 6-3 win over Borna Coric to reach the quarter-finals and move one step closer to seal the final standings. year n ° 1.
Djokovic can lock in first place by winning the title on Sunday.
Otherwise, Rafael Nadal could still overtake him mathematically, although the Spaniard is expected to enter a tournament in Bulgaria next month to do so.
Djokovic will face Hubert Hurkacz or Lorenzo Sonego in the quarterfinals on Friday.
Djokovic, who had not lost a set in three previous matches against Coric, saved two break points at 4-4 and one more in his next service game at 5-5.
Coric missed four set points in the 18-minute tiebreaker, including one on his own serve when he hit a wide forehand.
The Croatian saved two set points for Djokovic with aces, but hit a long backhand on his opponent’s third chance.
“Borna is a great fighter. He has a style of tennis similar to me. In the turn the backhand very solid, trying to create points with the forehand, ”said Djokovic in an interview on the pitch.
“He served very well, especially in the first set. It was very difficult for me to render a favor, ”said Djokovic, who also withstood a set point in his first round match.
“The tiebreak again, like yesterday against [Filip] Krajinovic, decided the game, I guess, ”he said.
Djokovic controlled the second set after Coric’s double fault against a 1-1 break point.
Djokovic didn’t give Coric another chance on his serve and took the win on his second match point.
“I’m really happy to stay focused and play my best at the right time,” said Djokovic.
Earlier, Stefanos Tsitsipas rallied to beat Jan-Lennard Struff 6-7 (3), 6-3, 6-4 and set up a second round match with Grigor Dimitrov.
Tsitsipas maintained his serve throughout the game, but still lost the first set in a tiebreaker before improving to 3-2 against his German opponent.
Medvedev advanced to the second round with a 6-3, 6-1 victory over Jason Lung, who replaced injured Alex De Minaur.
Additionally, Jannik Sinner beat Caspar Ruud 7-6 (2), 6-3 to set up a game against Andrey Rublev.