Britain’s Emma Raducanu is through to the last 16 of the Miami Open after opponent McCartney Kessler retired injured at the start of the second set.

Raducanu had been utterly dominant and needed just 30 minutes to take the first set 6-1.

An early break in the second set saw the 22-year-old race into a 3-0 lead, before American Kessler, 25, was forced to retire because of a back issue.

“I could tell something was up and it is hard to stay focused when your opponent is struggling,” Raducanu told Sky Sports. “I wish her a speedy recovery because she has been playing so well.

“I am happy with my focus, it is such a big part of tennis. I haven’t been at this stage of a tournament for a while.

“I returned really well and put pressure on the serve, imposing myself from the first game.”

Raducanu will play American Amanda Anisimova or 17-year-old Russian Mirra Andreeva in the next round.

Earlier, Australian Open champion and world number five Madison Keys was knocked out after a shock 6-4 6-2 defeat to Filipina wildcard Alexandra Eala.

The 19-year-old, who won the US Open girls singles title in 2022, is the first woman from the Philippines to beat a top-10 opponent since the professional Open era began in 1975.

The world number 140 has now knocked out two Grand Slam champions in Florida, having beaten 2017 French Open winner Jelena Ostapenko in the second round.

“Growing up it was tough. You didn’t have anyone from where you’re from to pave the way,” said Eala, who has been based to the Rafael Nadal academy in Mallorca since she was 13.

“Of course you had many people to look up to around the world, but I think – I hope this takes Filipino tennis to the next step.”

Eala will face Paula Badosa in the last 16 after the Spaniard beat Denmark’s Clara Tauson 6-3 7-6 (7-3).

Former champion and second seed Iga Swiatek is also through after a 7-6 (7-2) 6-1 win over Belgian 27th seed Elise Mertens.

The Polish world number two is the first player to reach the last 16 in 25 successive WTA 1000 events, a run stretching back to Cincinnati 2021.

Swiatek’s next opponent will be Ukraine’s Elina Svitolina, who beat Czech 15th seed Karolina Muchova 6-2 3-6 6-2.