Karolina Muchova scored another big-name upset in the second round of the Western & Southern Open, ousting No.7 seed Bianca Andreescu 6-4, 6-2 in 1 hour and 26 minutes.

It is the Czech's fifth victory over a Top 10 player in her career, and fourth this year. Previously, World No.23 Muchova defeated Karolina Pliskova and Ashleigh Barty en route to the Australian Open semifinals in February, and Naomi Osaka in the second round of Rome.

Muchova was joined in the last 16 of Cincinnati by No.11 seed Petra Kvitova, who was stellar form to beat Veronika Kudermetova 6-2, 6-4, and Elena Rybakina, who upset No.15 seed and last year's semifinalist Elise Mertens 6-3, 6-2.

Key to the match: As in her first-round win over Johanna Konta, Muchova's serve was crucial to her win. Her ace tally was down from 11 to four, and her delivery wasn't quite as watertight, but it was all in the scoreboard timing.

Muchova dropped her serve only twice - at the start of the match, when both players exchanged breaks as they settled into a first-time encounter, and when she was already up a double break in the second set.

But she found a series of service winners to hold off a surging Andreescu during a four-deuce tussle at 4-4 in the first set, saving one break point and served out both sets with rapid-fire holds, both of which featured an ace.

Andreescu's serve was also the strongest part of her game on her Cincinnati debut, and she came up with her share of clutch deliveries in tight moments. But it wasn't matched by her groundstrokes. The Canadian's forehand in particular leaked a cascade of errors as the second set went on.

Watch this: Muchova's fancy footwork upends Andreescu in Cincinnati

2021 Cincinnati

Shot of the match: Muchova and Andreescu are both renowned for the array of their shot-making, but much of this contest was characterised by short points dictated by the quality of their serving. But having lost the double break in the second set, Muchova brought out the magic to regain it.

Andreescu had dragged her into net with a drop shot and lofted a quality lob over her head. For once, Muchova seemed to be tangled up, unable to move into the right position in time to do anything with the ball. But some fancy last-minute footwork in the middle of the court enabled her to flick an unlikely pass past Andreescu to seal a 5-2 lead.

What's next: Muchova's strong 2021 continues apace as she extends her season record to 19-7. Having reached the Australian Open semifinals in February and backed that up with quarterfinal runs at Madrid and Wimbledon, she is now into the last 16 of a hardcourt WTA 1000 event for the first time. Next, she will face either No.10 seed Belinda Bencic or Shelby Rogers.

By contrast, 2019 US Open champion Andreescu - who is defending over half her points total this month - is still seeking to reignite her 2021. After an ankle sprain forced her to retire against Ashleigh Barty in the Miami final in March and Covid-19 ruled her out of much of the clay swing, Andreescu's record since returning has dropped to 4-6.

Kvitova, Rybakina move into last 16

Supreme serving was also seen from Kvitova and Rybakina after both dispatched dangerous opponents in straight sets.

Rybakina did not drop serve, faced break points in only one service game and conceded just three points behind her delivery in the second set. The Kazakh had split two previous hard-fought encounters with Mertens, but needed only 1 hour and 14 minutes to cruise past her this time.

Kvitova, twice a semifinalist in Cincinnati in 2012 and 2018, had been taken to three sets by Kudermetova in Madrid this May. The Russian's excellent early-season singles form has been seen more on the doubles court in recent months - she was Wimbledon runner-up and an Olympic semifinalist alongside Elena Vesnina - but played her part in a high-quality contest.

Key to the match: Ill-timed double faults played a significant role in Kudermetova's downfall. The World No.33 only committed four, but one came down break point at 2-3 in the first set, and another at 30-30 on the penultimate point of the set. By contrast, Kvitova successfully rattled through a series of dominant holds thanks to 10 aces.

Turning point: Kudermetova found a spell of scintillating form to peg Kvitova back from 4-1 to 4-4 in the second set - indeed, this passage of play saw both players conjure remarkable lobs at full stretch. But the Czech steadied herself and at 5-4, unleashed a barrage of scorching returns, finding a clean off backhand winner to seal her second match point.

What's next for Kvitova: A tantalising third-round clash against either No.6 seed Iga Swiatek, which would be a first-time meeting, or the crowd-pleasing variety of Ons Jabeur, against whom she has a 2-0 record.

Kvitova cruises past Kudermetova into Cincinnati last 16: Highlights

2021 Cincinnati