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Hyeon Chung is also through after an impressive victory over America’s Michael Mmoh, while Filip Krajinovic saw off Benoit Paire and Joao Sousa came from a set down to knock out Jared Donaldson.
In the ladies tournament, Venus Williams pulled off a brilliant win over Kiki Bertens in an extraordinary match to set up a last-16 tie against defending champion Johanna Konta.
Australia’s Ashley Barty was also a winner as she saw off Petra Martic in straight sets. Monica Puig followed up her shock win over Caroline Wozniacki with a victory over Maria Sakkari.
Here’s a look at all Sunday’s early scores. Full results and schedules are available from the tournament’s official website.
Joao Sousa beat Jared Donaldson 1-6, 6-3, 6-4
Hyeon Chung beat Michael Mmoh 6-1, 6-1
(21) Ashleigh Barty vs. Petra Martic 6-4, 6-3
(11) Johanna Konta vs (22) Elise Mertens 6-2, 6-1
(8) Venus Williams beat 5-7, 6-3, 7-5 (29) Kiki Bertens
(22) Filip Krajinovic beat Benoit Paire 6-3, 6-3
(2) Marin Cilic beat 7-5, 7-6 (4) Vasek Pospisil
Monica Puig beat Maria Sakkari 6-3, 7-5
Sunday Early Recap
Cilic was forced to work hard in the first set but proved his quality when it mattered to win the set 7-5. The Croatian forced a break point at 6-5 and took it, sending Pospisil the wrong way to surge ahead.
Pospisil had to save break points throughout the second set and was making little impression on Cilic’s serve.
Cilic had a chance at deuce at 6-5, but a stretching Pospisil pulled off one of the shots of the tournament to send the ball across court and past his opponent. Journalist Jose Morgado was impressed:
José Morgado @josemorgado
POINT OF THE TOURNAMENT, Vasek.
The Croatian then came through in the tie-break to progress in straight sets, although he was not at his best and will need to improve if he’s to go all the way.
Elsewhere, Konta made light work of Mertens as she eased through in straight sets in a little over an hour. Stuart Fraser at The Times was impressed with her performance:
Stuart Fraser @stu_fraser
An excellent performance from Johanna Konta, beating Australian Open semi-finalist Elise Mertens 6-2 6-1 in 65 minutes. Through to last-16 to face Venus Williams or Kiki Bertens #MiamiOpen
The defending champion was broken early in the first set but responded well. Mertens doubled-faulted four times in a single game to hand Konta a 3-2 lead.
Konta rarely looked back after that, as she served well and went for her shots, landing some big winners. The WTA showed how well she was playing:
.@JoKonta91 is in commanding control of this match. She has a double break in the first set against Mertens at the @MiamiOpen https://t.co/WNp2BXm3yn
Having secured the opening set, Konta then cruised into a 4-1 lead as she took control of the match. Mertens had no answer to her power and precision, as Konta lost just one game in the second set and completed the win.
The 26-year-old will now face Williams after she ousted Bertens in an incredibly entertaining match.
Williams roared in to a 5-0 lead after just 18 minutes, but Bertens produced an extraordinary comeback to take the first set 7-5, per the WTA:
Bravo @kikibertens! 👏👌 From 0-5 down against Venus Williams she takes the first set 7-5 at the @MiamiOpen! https://t.co/FqnPR41Cf7
The 37-year-old responded well to her slump initially but suffered another break in the second set and looked in real trouble at 3-2 with Bertens serving. However, she showed her champion qualities to hit back and take the second set 6-3 to force the decider.
Bertens took a 4-1 lead in the third set, but Williams responded again and forced her opponent to serve it out at 5-4. Williams saved two match points before breaking back to make it 5-5 and then showed real composure to take the set 7-5.
Morgado neatly summed up the match:
José Morgado @josemorgado
COMEBACK. Venus Williams saves 3 MPs, comes back from 3-5* 15-40 in the 3rd and beats Kiki Bertens 5-7, 6-3, 7-5 in 2h56 to reach the last 16 in Miami. She will face the defending champion Jo Konta tomorrow. https://t.co/xFiqpN9cti
It was an incredible effort and a superb victory for Williams, and it sets up an enticing clash against Konta. Sunday’s match will have taken a lot out of Williams, but her performance underlines how she is able to defy the odds. It may take something special to beat her.