Acapulco - Argentinian Juan Martin Del Potro defeated Dominic Thiem 6-2, 7-6 (7) on Thursday night to qualify for the semi-finals of the Mexican Open where he will play against German Alexander Zverev.
Zverev got a 6-4, 6-1 victory over American Ryan Harrison.
Kevin Anderson, from South Africa, will play against American Jared Donaldson in the other semifinal.
Del Potro now has a 4-0 record over Thiem.
The 21 year-old Donaldson needed only 53 minutes to beat Spaniard Feliciano Lopez 6-3, 6-1.
Anderson got a 7-6 (5), 6-4 over Hyeon Chung, from South Korea.
Results on Thursday in ATP and WTA Mexican Open in Acapulco (x denotes seeding):
Jared Donaldson (USA) bt Feliciano Lopez (ESP) 6-3, 6-1
Kevin Anderson (RSA x5) bt Chung Hyeon (KOR) 7-6 (7/5), 6-4
Juan Martin Del Potro (ARG x6) bt Dominic Thiem (AUT x3) 6-2, 7-6 (9/7)
Alexander Zverev (GER x2) bt Ryan Harrison (USA) 6-4, 6-1
Stefanie Vogele (SUI) bt Sloane Stephens (USA x1) 6-4, 5-7, 6-2
Rebecca Peterson (SWE) bt Shuai Zhang (CHN x4) 6-2, 6-1
Daria Gavrilova (AUS x3) bt Veronica Cepede (PAR) 6-4, 4-6, 6-2
Lesia Tsurenko (UKR x7) bt Kristina Mladenovic (FRA x2) 6-2, 6-2