Madrid -Kei Nishikori will face Stan Wawrinka in the third round of the Madrid Open after battling past Bolivian qualifier Hugo Dellien on Wednesday.
Nishikori needed just over two hours to win 7-5, 7-5 after Dellien saved seven set points during an impressive fightback from 5-1 down in the opening set.
The Japanese will go up against Wawrinka on Thursday for a place in the quarter-finals. The winner could play Rafael Nadal.
Wawrinka beat Argentina's Guido Pella 6-3, 6-4, with a break in each set proving enough for the three-time Grand Slam champion.
Nishikori has lost his last two meetings with Wawrinka, including a three-set defeat in Rotterdam in February, when his Swiss opponent went on to reach his first final since undergoing knee surgery in 2017.
The pair have reached 12 grand slam semi-finals between them.
Nishikori's compatriot and world number one Naomi Osaka is through to the quarter-finals of the women's tournament for the first time after she eased past Belarusian Aliaksandra Sasnovich 6-2, 6-3.
Osaka pulled out of the semi-finals in Stuttgart last month with an abdominal injury but has said she is no longer feeling discomfort during matches.
"The ab injury was always sort of in the back of my mind, but that was more in the first round and now I feel fine, so that's great," Osaka said.
"I'm at a really good place right now. I feel like I'm having fun playing tennis again which is always a good thing for me. I always play well if I have that mentality."
In the last eight, the two-time major champion will face either Switzerland's Belinda Bencic who beat Ukraine's Kateryna Kozlova 6-0, 6-2.
A potential semi-final foe for Osaka is world number three Simona Halep, who annihilated Slovakian Viktoria Kuzmova 6-0, 6-0 in 44 minutes.
Halep is chasing her third Madrid title after winning the tournament in 2016 and 2017.
Results from the ATP and WTA tournaments in Madrid on Wednesday (x denotes seeding):
Jeremy Chardy (FRA) bt Diego Schwartzman (ARG) 6-1, 6-2
Laslo Djere (SRB) bt Juan Martin del Potro (ARG x7) 6-3, 2-6, 7-5
Gael Monfils (FRA x15) bt Marton Fucsovics (HUN) 1-6, 6-4, 6-2
Fabio Fognini (ITA x10) bt John Millman (AUS) 6-2, 6-2
Kei Nishikori (JPN x6) bt Hugo Dellien (BOL) 7-5, 7-5
Stan Wawrinka (SUI) bt Guido Pella (ARG) 6-3, 6-4
Frances Tiafoe (USA) bt Philipp Kohlschreiber (GER) 6-4, 3-6, 6-3
Rafael Nadal (ESP x2) bt Felix Auger-Aliassime (CAN) 6-3, 6-3
Naomi Osaka (JPN x1) bt Aliaksandra Sasnovich (BLR) 6-2, 6-3
Belinda Bencic (SUI) bt Kateryna Kozlova (UKR) 6-0, 6-2
Simona Halep (ROU x3) bt Viktoria Kuzmova (SVK) 6-0, 6-0
Ashleigh Barty (AUS x9) bt Yulia Putintseva (KAZ) 4-6, 6-1, 6-2
Kiki Bertens (NED x7) bt Anastasija Sevastova (LAT x12) 6-1, 6-2