Katie Boulter exits Miami Open after loss to Victoria Azarenka

Boulter had broken new ground with victory over Beatriz Haddad Maia in the previous round to reach the last-16 of the tournament for the first time, but saw her journey in Florida end after she was ground down by her veteran opponent.

A marathon first set went the way of former world number one Azarenka and it proved pivotal with Boulter unable to keep up her level in set two before she lost 7-5 6-1.

Two-time Australian Open champion Azarenka looked on course to cruise past the recent San Diego Open winner when she established a 5-2 lead in the first set.

World number 30 Boulter had already faced a string of break points by this point, but had to save a number of set points in what proved a decisive eighth game.

It spurred Boulter on and she broke back against the Belarusian before she held again to level at 5-5.

However, with a tie-breaker on the horizon, Azarenka showed her experience to claim another break against the Briton before she closed out a 71-minute first set.

The momentum had firmly swung now and Azarenka went on to break Boulter at the start of the second.

Another break followed before another poor service return by Boulter sealed Azarenka's passage into the last eight where she will face Yulia Putintseva.

World number one Iga Swiatek's hopes of adding the Miami title to her Indian Wells success were ended as she was dumped out 6-4 6-2 by 14th seed Ekaterina Alexandrova.

Alexandrova broke Swiatek in the opening game as she overpowered the Pole from the baseline and with her service.

"Second quarter-final here, second year in a row," Alexandrova said. "Beating Iga after so many tries and she's number one. It's the first time I beat number one. All three things are very special to me.

"I think when it goes in its very good but sometimes it's not working. But today it worked."

American Jessica Pegula awaits in the last eight after the fifth seed beat Emma Navarro 7-6 6-3.

Elsewhere, world number 23 Caroline Garcia beat Coco Gauff 6-3 1-6 6-2 while former Wimbledon champion Elena Rybakina joined Garcia at the quarter-final stage with a 6-3 7-5 victory over Madison Keys.