Serena Williams is firmly in the sights of Angelique Kerber after the German world number two advanced to the semi-finals of the Western and Southern Open.
Kerber rallied to beat fellow seed Carla Suarez Navarro in three sets in Cincinnati on Friday, with WTA's top ranking edging closer.
Next up for the Australian Open champion is last year's runner-up Simona Halep, who edged Agnieszka Radwanska.
Spanish fourth seed Garbine Muguruza eased past Timea Babos, while Karolina Pliskova outlasted Svetlana Kuznetsova.
TOP RANKING LOOMS FOR KERBER
Victory at the Premier tournament would see second seed Kerber become number one in the world, dethroning 22-time grand-slam champion Williams, who has topped the standings for 183 weeks.
And Kerber's top-ranking bid remains on track after prevailing 4-6 6-3 6-0 against ninth-seeded Spaniard Suarez Navarro.
Kerber, though, was forced to do it the hard way after tallying 17 unforced errors in a disappointing opening set.
Suarez Navarro eventually faded in the soaring temperatures, with Kerber breaking for a 4-2 lead in the second, as she levelled the match and the 2016 Olympic Games silver medallist as she powered into the final four.
HALEP REACHES SECOND SUCCESSIVE SEMI IN CINNCINATI
Another year at the Western and Southern Open, and another semi-final berth for third seed Halep.
A finalist in 2015, Halep saw off the challenge of fifth seed Radwanska 7-5 6-1 in one hour, 31 minutes.
The first set was a tight affair but Halep held firm, saving seven of 10 break points, while converting all four of her own, to get the better of the Pole.
MUGURUZA A CLASS ABOVE
French Open winner and fourth seed Muguruza barely raised a sweat as she defeated Hungarian qualifier Babos 6-4 6-3.
Victory was never in doubt for Muguruza, who did not drop serve and won three of nine break points.
Awaiting Muguruza in the semis is 15th seed Pliskova, who beat Kuznetsova 6-3 4-6 6-2.
PLISKOVA RELISHING FINAL-FOUR CLASH
After earning a showdown with Muguruza, Pliskova said: "Any semi-final is great because you have the chance to get to the final, so I'll just do my best to prepare for the next match."
Kerber always believed against Suarez Navarro, adding: "I was still thinking that I can turn around the match even after losing the first set and going down a break early in the next set."
KERBER AND HALEP TAKE CENTRE STAGE
Saturday's semi-final between Kerber and Halep - which pits the second seed against the third - is the pick of the action. The schedule, however, gets underway with Pliskova facing Muguruza in the afternoon.