Kevin Anderson survived two match points to spring an upset on Nick Kyrgios at the Chengdu Open, but top seed Dominic Thiem proved too strong for qualifier Wu Di in China.
Big-serving Anderson was already a set down when he trailed 6-4 in a second-set tie-break, but the South African fought back brilliantly to defeat to controversial Australian 3-6 7-6 (8-6) 6-2 on Thursday.
Anderson fired down 24 aces against the second seed and dropped just eight points on first serve en route to setting up a quarter-final with Viktor Troicki, who defeated Marco Baghdatis 6-3 4-6 6-2.
On the other side of the draw, Thiem - who remains well in contention to qualify for the ATP World Tour Finals next month - was too good for Wu in a 6-4 6-4 win and next faces Albert Ramos-Vinolas, who needed three sets to see off Lu Yen-hsun.
At the Shenzhen Open, top seed Tomas Berdych - who is one place outside the World Tour Finals top eight - displayed his battling qualities to defeat Mikhail Kukushkin 7-6 (9-7) 7-6 (7-4).
The Czech next faces compatriot Jiri Vesely following his 7-6 (7-2) 6-3 win over Inigo Cervantes.
Bernard Tomic is into the last eight after coming through a tough three-setter against Ryan Harrison, and the third seed will face Thomaz Bellucci for a spot in the semi-finals after the Brazilian defeated Thomas Fabbiano 7-6 (7-2) 7-6 (7-4).