Puerto Rico's Monica Puig is on the verge of her country's first Olympic gold medal after beating Petra Kvitova to seal a place in the final of the women's tennis singles.
The competition in Rio was blown wide open by favourite and reigning champion Serena Williams' early exit and Puig may transpire to be the main beneficiary after beating her Czech opponent 6-4 1-6 6-3.
She will now face Angelique Kerber in the decider, after a display of textbook returning earned the German a 6-3 7-5 victory over American Madison Keys.
In the quarter-finals of the men's singles, Kei Nishikori and Gael Monfils toughed out an epic, the Japanese eventually coming through in a third-set tie-break.
Nishikori will next meet defending Olympic champion Andy Murray, who dug deep in the face of a fightback from American Steve Johnson - progressing to the last four courtesy of a 6-0 4-6 7-6 (7-2) victory.
An action-packed day for Rafael Nadal ended with a second career gold medal, as he and partner Marc Lopez saw off Romania's Florin Mergea and Horia Tecau in the men's doubles final, while United States duo Johnson and Jack Sock won a North American battle with Canadians Daniel Nestor and Vasek Pospisil for bronze.
Beijing 2008 singles champion Nadal had earlier reinforced his solo prowess by beating Brazil's home hope Thomaz Bellucci, battling back from losing the first set to win 2-6 6-4 6-2 and setting up a semi-final with Juan Martin Del Potro, a straight-sets victor over Roberto Bautista Agut.
MATCH OF THE DAY
Nishikori's thrilling quarter-final against Monfils certainly had plenty of drama, the Frenchman serving a double fault on his way to blowing three match points in the deciding tie-break.
But it was the women's side of the competition that really caught the imagination as Puig, ranked 34th in the world and with just one WTA title to her name, put herself on the brink of history for her country.
Her prospects did not look good initially at the Olympic Tennis Centre as Kvitova stormed into a 3-0 lead in the opening set, but Puig dug deep and showed greater resolve on the key points to mount a superb fightback.
The second set was one-way traffic, with Kvitova storming through 6-1, but that did not deter Puig as she displayed superb resolve to win a mammoth rally en route to taking the decider 6-3.
QUOTES OF THE DAY
"It would be unbelievable and it would be the biggest honour in the world. But I'm doing it more for my country." - Puig reflects on what it would mean to Puerto Rico to have an Olympic champion.
"As the days go on, you start to feel a little bit better and loosen up a little bit and play better. For me it has nothing to do with having won the gold in London. For me it's about trying to win more medals for the country and the team" - Great Britain's Murray on the challenge of trying to defend his men's singles title.
Three medals will be up for grabs on Saturday, with the women's singles final the undoubted highlight.
As well as the gold medal match between Puig and Kerber, Kvitova and Keys will do battle for bronze, while the women's doubles third-place match will be an all-Czech affair, as Lucie Safarova and Barbora Strycova take on Andrea Hlavackova and Lucie Hradecka.