Cape Town - South Africa's top tennis player, Kevin Anderson, lost in the first round of the Cincinnati Masters on Tuesday.
Anderson went down to Alexandr Dolgopolov of the Ukraine, losing in straight sets with a 6-4, 7-6 (8/6) scoreline.
On Monday, Anderson had climbed five spots to No 27 on the official ATP rankings.
It followed his run to the quarter-finals of last week's Montreal Masters where he was defeated 7-5, 6-4 by eventual champion Alexander Zverev of Germany.
Anderson, 31, also lost to Zverev the previous week in the Washington final - a result that catapulted him from No 45 to No 32 in the rankings.
Anderson, whose highest ranking to date has been No 10 in 2015, will now shift his focus to the US Open which starts on August 28.
Results on Tuesday from the WTA and ATP Cincinnati Masters tournament (x denotes seeding):
Men
Second round
John Isner (USA x14) bt Tommy Paul (USA) 6-3, 6-3
Ivo Karlovic (CRO) bt Jo-Wilfried Tsonga (FRA x8) 6-4, 7-6 (11/9)
Dominic Thiem (AUT x3) bt Fabio Fognini (ITA) 6-3, 6-2
First round
Nick Kyrgios (AUS) bt David Goffin (BEL x9) 6-2, 6-3
Alexandr Dolgopolov (UKR) bt Kevin Anderson (RSA) 6-4, 7-6 (8/6)
Juan Martin del Potro (ARG) bt Tomas Berdych (CZE x10) 3-6, 7-6 (7/1), 6-0
Karen Khachanov (RUS) bt Diego Schwartzman (ARG) 6-1, 1-6, 6-3
Albert Ramos-Vinolas (ESP) bt Mikhail Youzhny (RUS) 6-2, 3-6, 6-3
David Ferrer (ESP) bt Steve Johnson (USA) 6-1, 5-7, 6-3
Yuichi Sugita (JPN) bt Jack Sock (USA x13) 7-5, 6-4
Nikoloz Basilashvili (GEO) bt Borna Coric (CRO) 6-3, 7-6 (7/5)
Jared Donaldson (USA) bt Roberto Bautista Agut (ESP x12) 7-6 (7/5), 6-3
Pablo Carreno Busta (ESP x11) bt Paolo Lorenzi (ITA) 6-3, 6-3
Adrian Mannarino (FRA) bt Robin Haase (NED) 2-6, 7-6 (10/8), 6-2
Women
Second round
Simona Halep (ROM x2) bt Taylor Townsend (USA) 6-4, 6-1
Johanna Konta (GBR x7) bt Kiki Bertens (NED) 6-3, 6-3
Garbine Muguruza (ESP x4) bt Beatriz Hadded Maia (BRA) 6-2, 6-0
First round
Ashleigh Barty (AUS) bt Varvara Lepchenko (USA) 6-4, 6-4
Natalia Vikhlyantseva (RUS) bt Donna Vekic (CRO) 6-3, 2-6, 6-3
Dominika Cibulkova (SVK x11) bt Ana Konjuh (CRO) 5-7, 7-5, 6-2
Venus Williams (USA x9) bt Alison Riske (USA) 6-2, 6-0
Aleksandra Krunic (SRB) bt Jelena Ostapenko (LAT x12) 6-4, 6-2
Julia Goerges (GER) bt Agnieszka Radwanska (POL x10) 6-4, 6-4
Alize Cornet (FRA) bt Catherine Bellis (USA) 7-6 (7/5), 3-6, 6-2
Anastasja Sevastova (LAT x15) bt Peng Shuai (CHN) 3-6, 6-4, 6-2
Elena Vesnina (RUS) bt Caroline Garcia (FRA) 4-6, 6-4, 6-4
Francoise Abanda (CAN) bt Magda Linette (POL) 3-6, 6-4, 6-2
Sloane Stephens (USA) bt Lucie Safarova (CZE) 6-4, 7-6 (7/5)
Ekaterina Makarova (RUS) bt Barbora Strycova (CZE) 6-4, 6-1