Aryna Sabalenka defeated Romania's Jaqueline Cristian 6-1 6-4 in one hour and 25 minutes to reach the Round of 16 of the Madrid Open on Saturday.
Sabalenka is the defending champion in the Spanish capital and will next face Naomi Osaka for a place in the quarter-finals.
The world No 1, who has now won 14 matches in a row, said after: "Especially in the first set, that was incredible level from me.
"I even hit a one-handed backhand, which is a little bit crazy. I think that was the shot of my life, that's for sure."
Elsewhere, Venus Williams claimed her first victory since the US Open with doubles success alongside Great Britain's Katie Boulter.
Williams accepted Boulter's request to play together at the Madrid Open, and the scratch pairing fought back from a set down to beat China's Jiang Xinyu and Xu Yifan 4-6 6-3 (10/7) in the opening round.
Williams, 45, is on a 10-match losing streak in singles after falling again in the first round here, while she had not won a doubles match since reaching the quarter-finals of the US Open with Leylah Fernandez last summer.
The pair clearly enjoyed the experience, with Boulter saying: "It was great, it was so much fun. Obviously just to have the privilege of being on court and also being on the same side of the net - I don't want to be on the other side of the net.
"It was really nice to get the chance to play with Venus and I enjoyed every minute of it."
Iga Swiatek's struggles continued with a tearful withdrawal during her third-round match against Ann Li at the Madrid Open.
The former world No 1, who is yet to advance beyond the quarter-finals at any event this season, revealed afterwards she is battling a virus and she had her temperature and blood pressure checked after losing the opening two games of the deciding set.
After taking pills, Swiatek initially continued, but looked lethargic and pulled the plug trailing American Li 6-7 (4) 6-2 0-3 0-30 before walking off the court in tears.
"The last two days were pretty terrible," said the Pole. "I think I have some virus.
"It's been some hours fine, some hours pretty bad. I heard there is something going on between players, that the virus is somewhere on site. I'm sure I'll be fine in a couple of days, but I had zero energy.
"I just felt really bad physically, and yesterday, even worse. I thought maybe today it's going to be better - maybe it was, but not enough to play a match."
Swiatek looked to have turned the contest around after losing a tight opening set but it was no surprise when she called it a day given her demeanour in the third set.
Asked if she considered not taking to the court at all, the fourth seed said: "I knew that it was going to be hard but I still wanted to try.
"In the third set I started feeling a little bit dizzy and not really coordinated. I couldn't really drink anything because I just felt like I'm full constantly, and the energy went down drastically."
Swiatek will now focus on recovering before turning her thoughts to the Italian Open in Rome next month, where she will hope to find form under new coach Francisco Roig ahead of Roland Garros.
"It's sad for me that I can't play because I was feeling really good with my game, and I was moving forward in the process," she said.
"The tournament has just started. I couldn't even compete today, so it's disappointing."
In the men's singles, second seed Alexander Zverev dropped a set against Argentina's Mariano Navone but recovered to claim a 6-1 3-6 6-3 victory.
Defending champion Casper Ruud raced to a 6-0 6-1 win over Spain's Jaume Munar while third seed Felix Auger-Aliassime is also through to the third round.
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