Katie Boulter recorded her seventh straight win on the WTA Tour as Camila Osorio retired from their Merida Open clash.
The British No 3 arrived in Mexico on the back of winning the Ostrava Open and overcame issues with her serve to edge past Beatriz Haddad Maia in the opening round.
Boulter, 29, had taken the first set 6-3 when Colombian Osorio called for the physio and decided against continuing the contest.
The victory sees Boulter progress to the last eight, where she will either face top seed Jasmine Paolini or Australia's Priscilla Hon.
Boulter said in her courtside interview: "Obviously we really don't want to see women with injuries, it's been pretty tough recently. I've seen a lot of people with them and I've been through them myself so I know how difficult it is.
"It's really not fun so I wish her the very best and I hope to see her next week in Indian Wells and hopefully it's something small."
She added: "Obviously, I really love playing in front of a lot of people so it's really nice to have everyone out here supporting the tournament. I'm just happy to be out here and playing more matches."
Britain's Fran Jones made a first-round exit at the ATX Open in Austin as Peyton Stearns recovered from a set down to edge a closely-fought contest.
Home favourite Stearns reeled off the first three games, but Jones took the next seven to win the first set and hold at the start of the second.
But the 25-year-old began to struggle with her serve and was broken in six of her last seven service games as Stearns wrapped up a 3-6 6-3 6-2 victory.
It was Jones' first match since she left the court in tears at the Australian Open after pulling out of her opening match with a leg injury.
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