16:30 CET - Welcome back to Flashscore's Tennis Tracker for a big day of preparation ahead of the final Grand Slam of the year.
In the men's draw, it is wide open to see who will lift the title on Sunday. Flavio Cobolli is the highest-ranked player at 10 in the world, but all four left in the tournament have a shot at the crown.
The Italian takes on Arthur Fils from 19:30 CET, with Fils winning both of their encounters in the past, both in straight sets.
In the other semi-final from 01:30 CET on Sunday morning is an all-American affair between Frances Tiafoe and Brandon Nakashima.
Nakashima has been on a tear in recent weeks. He made the final in Montreal last week, falling just short of the win, and he beat Taylor Fritz in his last match to make the final four.
Tiafoe, though, will be a stern test. He leads the head-to-head 7-1, whilst he has won seven of his 10 matches against fellow Americans this year.
Meanwhile, in the women's draw, three stars and one underdog will take to the court.
The blockbuster clash is undoubtedly Jessica Pegula vs Iga Swiatek. The former number one, Swiatek, has seen her form improve in recent weeks, winning the Canadian Open last time out.
It's been a tough run in Cincinnati for Pegula. She needed three sets to see off Amanda Anisimova, and she knows it will be another tough test today, with the head-to-head record favouring the Pole 7-5.
In the other semi-final, Coco Gauff faces up-and-coming Czech star Sara Bejlek, who took down former Australian Open champion Madison Keys in the last round.
This is just her second WTA semi-final, and she could prove a problem for the American.