Nishikori defeated by 'stronger' Nishioka in all-Japanese contest
Cincinnati - Kei Nishikori lost to fellow Japanese Yoshihito Nishioka 7-6 (7/2), 6-4 on Wednesday in the second round of the ATP Cincinnati Masters.
The sixth seed went down to his 77th-ranked compatriot, who came through qualifying, in just over 90 minutes.
"It was a tough match for me. I think he played good tennis, served well," Nishikori said.
"I was happy to play him for the first time. It's good to see he's getting stronger, growing up. He was already good, he gets a lot of balls back and has good defence."
Nishikori has never advanced beyond the third round at the US Open warm-up event.
Nishioka will next face Australia's Alex de Minaur, who was a 7-6 (7/3), 6-4 winner over American wildcard Reilly Opelka.
Results on Wednesday in the WTA/ATP Cincinnati Masters (x-denotes seeding):
Lucas Pouille (FRA) bt Denis Shapovalov (CAN) 6-4, 6-4
Andrey Rublev (RUS) bt Stan Wawrinka (SUI) 6-4, 6-4
Daniil Medvedev (RUS x9) bt Benoît Paire (FRA) 7-6 (7/2), 6-1
Jan-Lennard Struff (GER) bt Stefanos Tsitsipas (GRE x5) 6-4, 6-7 (5/7), 7-6 (8/6)
Miomir Kecmanovic (SRB) bt Alexander Zverev (GER x7) 6-7 (4/7), 6-2, 6-4
Diego Schwartzman (ARG) bt Radu Albot (MDA) 6-4, 6-2
Richard Gasquet (FRA) bt Federico Del Bonis (ARG) 7-5, 7-6 (7/1)
Yoshihito Nishioka (JPN) bt Kei Nishikori (JPN x6) 7-6 (7/2), 6-4
Alex De Minaur (AUS) bt Reilly Opelka (USA) 7-6 (7/3), 6-4
David Goffin (BEL x16) bt Guido Pella (ARG) 6-1, 7-5
Adrian Mannarino (FRA) bt Mikhail Kukushkin (KAZ) 6-1, 6-3
Roberto Bautista Agut (ESP x11) bt Frances Tiafoe (USA) 6-3, 3-6, 6-1
Karen Khachanov (RUS x6) bt Nick Kyrgios (AUS) 6-7 (3/7), 7-6 (7/4), 6-2
Ashleigh Barty (AUS x1) bt Maria Sharapova (RUS) 6-4, 6-1
Anett Kontaveit (EST) bt Iga Swiatek (POL) 6-4, 7-6 (7/2)
Aryna Sabalenka (BLR x9) bt Saisai Zheng (CHN) 6-4, 6-3
Karolína Plíšková (CZE x3) bt Yafan Wang (CHN) 6-1, 6-3
Rebecca Peterson (SWE) bt Veronika Kudermetova (RUS) 2-6, 7-5, 6-2
Svetlana Kuznetsova (RUS) bt Dayana Yastremska (UKR) 4-6, 7-6 (9/7), 6-2
Donna Vekic (CRO) bt Victoria Azarenka (BLR) 6-2, 7-5
Madison Keys (USA x16) bt Darya Kasatkina (RUS) 6-4, 6-1
Simona Halep (ROU x4) bt Ekaterina Alexandrova (RUS) 3-6, 7-5, 6-4
Elina Svitolina (UKR x7) bt Elise Mertens (BEL) 6-4, 6-1
Sofia Kenin (USA) bt Zarina Diyas (KAZ) 6-4, 6-1
Su-Wei Hsieh (TPE) bt Jennifer Brady (USA) 7-6 (11/9), 6-3
Naomi Osaka (JPN x2) bt Aliaksandra Sasnovich (BLR) 7-6 (7/3), 2-6, 6-2
Sloane Stephens (USA x8) bt Yulia Putintseva (KAZ) 2-6, 6-4, 6-3