Auckland - World No 13 Denis Shapovalov crashed out of the ATP Auckland Classic on Thursday, beaten in straight sets by French qualifier Ugo Humbert.
There was only one break in each set of the evenly contested clash with Humbert winning 7-5, 6-4, clinching the victory with the Canadian's sixth double fault.
"I'm really, really, happy, it's one of the biggest wins of my career," the 57th-ranked Humbert said as he advanced to a semi-final showdown big-serving American John Isner.
"I tried to play each ball, I tried to stay focused and my plans were working."
Isner survived on his thunderous serve with an impressive 25 aces to overcome Kyle Edmund in the opening quarter-final.
While Edmund had the better of the fourth seed for much of the match, Isner served his way out of trouble when it mattered and the Briton was unable to convert any of his nine break points.
Both sets went to a tiebreak before the American won 7-6 (7/5), 7-6 (7/5) and expressed relief at making the final four.
"I know I was a bit fortunate to win today, that's how tennis goes, but I'm happy I'm in the semi-finals," said the two-time Auckland champion who holds the world record for the most aces in a match with 113 against Frenchman Nicolas Mahut at Wimbledon two years ago.
"That match point, I played it very aggressively and very well. Winning a match like this can give me a lot of confidence going forward for the rest of this tournament, the Australian Open and for the rest of the year."
Fifth-seed Benoit Paire battled through his third three-setter in as many matches to beat Australian John Millman.
The Frenchman made a nervous start, dropping his first serve and losing the opening set 6-3.
But once he added a touch of finesse to his power game, drawing Millman forward with delicate drop shots, Paire won the next two sets 6-1, 6-4.
Hubert Hurkacz, the 20-year-old sixth seed from Poland, outlasted the 38-year-old Feliciano Lopez in a titanic three-set battle to determine Paire's semi-final opponent.
After taking the first set 6-4, Hurkacz held three match points at 6/3 in the second set tie break but Lopez, who had knocked out top seed Fabio Fognini in three sets the previous day, refused to quit.
He won three consecutive points to draw level and the pair then went point for point until Lopez triumphed at 13/11.
Hurkacz broke immediately at the start of the deciding set and held the advantage until the end to complete a 6-4, 6-7 (11/13), 6-4 victory.
Results from the quarter-finals of the ATP Auckland Classic tennis tournament on Thursday:
John Isner (USA x4) bt Kyle Edmund (GBR) 7-6 (7/5), 7-6 (7/5)
Ugo Humbert (FRA) bt Denis Shapovalov (CAN x2) 7-5, 6-4
Benoit Paire (FRA x5) bt John Millman (AUS) 3-6, 6-1, 6-4
Hubert Hurkacz (POL x6) bt Feliciano Lopez (ESP) 6-4, 6-7 (11/13), 6-4
John Isner (USA) vs Ugo Humbert (FRA)
Benoit Paire (FRA x 5) vs Hubert Hurkacz (POL x6)