Top seed David Ferrer was bundled out of the Shenzen Open second round by Serb Viktor Troicki on Thursday.
To compound the Spaniard's misery, the 6-3 6-4 defeat will not help his chances of reaching the year-ending ATP World Tour Finals in London.
Ferrer, 32, is currently seventh in the race to qualify for the Nov. 9-16 event in London. Novak Djokovic, Roger Federer and Rafa Nadal have already booked three of the eight spots for the singles.
Tomas Berdych is almost neck and neck with Ferrer, just 25 points behind in eighth spot before this week's tournaments, but ninth-placed Milos Raonic is not far behind, with Grigor Dimitrov and Andy Murray on his heels.
World number 174 Troicki fired 13 aces to canter to victory in just 66 minutes, his first over world number five Ferrer in four matches.
ATP Race to London standings (top eight qualify)
1. Novak Djokovic 8150-qualified
2. Roger Federer 7020-qualified
3. Rafa Nadal 6645-qualified
4. Stanislas Wawrinka 4795
5. Marin Cilic 3935
6. Kei Nishikori 3675
7. David Ferrer 3535
8. Tomas Berdych 3510
9. Milos Raonic 3440
10. Grigor Dimitrov 3335
11. Andy Murray 3155
12. Jo-Wilfried Tsonga 2650 – Reuters