The Australian, fresh from his heroics at Wimbledon where he reached the fourth round of a grand slam for the first time, triumphed in Newport, Rhode Island on Thursday after his match against the young Canadian star had to be suspended the previous evening because of darkness.
The Brisbane man had found himself in a precarious situation when the match was suspended on Wednesday, having to return to serve at 5-6 down in the deciding set to stay in the match.
And he diced with disaster on the resumption when Auger-Aliassime earned match point at 30-40.Â
But the Australian won the next three points against the world No.9 to take the match into a tiebreak decider and then earned a decisive mini-break at 4-3 up before going on to earn his first-ever victory over a top-10 player.
It means an Australian will definitely make the semi-finals of the only ATP tour grass-court event to be staged outside Europe, with Kubler set to face Sydneysider James Duckworth in the last-eight on Friday.
It also continued the 29-year-old Kubler's amazing late-career renaissance as Queensland's former world junior No.1, whose career has been interrupted by six knee surgeries, has now won 24 of his last 28 matches and reached his first-ever ATP quarter-final.
Not only was he the last Australian man standing at the French Open after getting through qualifying, he's also won a Challenger tournament and reached the final of another in the US, before winning six matches at Wimbledon, including a win over seed Dan Evans on the way to the last 16.
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