Poland's Iga Swiatek says becoming world number one is "surreal" after a second-round win in Miami means she will take the mantle from Ashleigh Barty, who has retired from the sport.
Three-time Grand Slam winner Barty, 25, announced her shock retirement earlier this week, saying she would "chase other dreams" instead.
She had been world number one for 114 consecutive weeks.
Swiatek, 20, is the first Polish player to sit at the top of the rankings.
"The thing is, I never really imagined that moment because, truth to be told, I was working day-by-day and playing tennis well," Swiatek said.
"But I never had the strong belief that it can actually happen. So, it's even more surreal for me."
After winning the Indian Wells title last week - which took her to number two in the world - Swiatek extended her career-best 12-match winning streak with a 6-2 6-0 win against Viktorija Golubic of Switzerland in the Miami Open.
The victory guaranteed Swiatek, who burst to prominence by winning the 2020 French Open, would take over from Barty when the new ranking is released on April 4.
Speaking about the prospect of Swiatek becoming number one following her retirement, Barty said: "If it is Iga, there is no better person. She's an incredible person, a great player. The way she's brought this fresh, fearless energy on to the court has been incredible.
"She thoroughly deserves it. I hope she can take it and still be her, do it her own way, and really chase what she's after in her career and her dreams."
Earlier on Friday, Czech 16-year-old Linda Fruhvirtova, ranked 279, secured her place in the third round in Miami after beating world number 24 Elise Mertens.
American Coco Gauff and the Czech Republic's two-time Wimbledon champion Petra Kvitova also progressed with comfortable wins.
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