Japan's top seed Kei Nishikori was bundled out in the second round of the Dubai Championships on Wednesday, losing 7-5, 5-7, 6-2 to unfancied Hubert Hurkacz.
The Polish number one ranked 77th in the world handed the favourite his exit papers as Nishikori played the gulf event for the first time.
He came to the emirate with an early season title from Brisbane, where he claimed his first trophy since 2016.
Hurkacz moved into his first ATP quarterfinal after scoring his first career victory over a Top 10 opponent, needing just over two hours completing the upset.
The outsider caught Nishikori with a late break in the opening set but the favourite looked like making up ground in the second when he moved from 4-0, 5-2 up.
But Nishikori failed on four occasions to serve it out before squeaking through with a break for 6-5 followed by a serve hold to make it a set each after 92 minutes.
Hurkacz finished the job as he claimed the final set to advance, winning with six breaks of serve from seven chances.
Nadal through
Rafael Nadal powered into the second round at the Mexican Open in Acapulco on Tuesday, breezing past Germany's Mischa Zverev in straight sets to advance to a meeting with Australia's Nick Kyrgios.
World number two Nadal, playing in his first event since being thrashed by Novak Djokovic in last month's Australian Open final, was always in control during a 6-3, 6-3 victory.
The 17-time Grand Slam champion completed the victory in 1hr 20min at Acapulco's Princess Mundo Imperial venue, defeating his 76th ranked opponent with ease.
The tournament top seed seized the advantage in the opening set, scoring a break to go 3-1 ahead with a delicate lob that left Zverev floundering.
With Nadal's superior variety proving too much for Zverev, the Spaniard quickly wrapped up the opening set.
The second set went with serve until the seventh game, when a wild forehand from Zverev sailed wide to give Nadal the break for a 4-3 lead. Zverev hung his head following the miscue, seemingly realising there was no way back.
Nadal then held for a 5-3 lead and wrapped up victory in the ninth game, moving to match point when Zverev could only plop a return tamely into the net.
Elsewhere on Tuesday, Zverev's younger brother Alex had little difficulty in advancing to the second round, defeating Australia's Alexei Popyrin 6-3, 6-3.
Second seed Zverev's service game overwhelmed Popyrin, with the German hammering down 13 aces en route to victory.
Australia's Kyrgios meanwhile was made to work hard for victory in his win over Italy's Andreas Seppi, battling into the second round with a 6-3, 7-5 win.
Third seed John Isner of the United States also had a testing opening game, needing three sets to subdue France's Adrian Mannarino 6-3, 4-6, 6-3.