Argentine Juan Martin del Potro came from 4-1 down in the second set to beat top seed Robin Soderling 6-4, 7-5 here on Friday in the quarter finals of the ATP-WTA Estoril Open.
Del Potro, the 2009 US Open champion who missed most of last year after wrist surgery, will play fellow South American Pablo Cuevas of Uruguay, who put out Brazil's sixth seed Thomaz Bellucci 6-4, 6-2, on Saturday.
Del Potro led 6-4 but trailed in the second when heavy rain arrived to interrupt afternoon play as he faced the Swede whom he had never played on clay.
After the storms passed, del Potro - who saved five of six break points and served six aces - came back out in fading light and broke Soderling twice to win after just under two hours of play.
"It was very tough mentally today," said Del Potro, who was recording his 23rd win of the season.
"You had to keep focus on court, in the locker room, in the player's lounge all during the delay. But I managed that well.
"I really wanted to win and I'm pleased with how I did. it was a good victory for me today. I trained last week with Pablo (Cuevas) between Buenos Aires and here.
"I could not win a set with him in practise, so I know our match will be tough."
On the women's side, unseeded duo Kristina Barrois and Anabel Medina Garrigues will meet in the final.
The 29-year-old Barrois flew the flag for Germany as she reached the second final of her career, defeating Swede Johanna Larsson 7-6 (7/2), 6-4.
Barrois will aim to win her first title on Saturday against Spaniard Medina Garrigues, who beat Monica Niculescu of Romania, 6-1, 6-3.
Barrois, a quarterfinalist last week in Stuttgart, said that her recent experiences in playing big matches and top players is boosting her confidence.
"I played some good matches last week in Stuttgart, they gave me the belief that I can face Top 5 players. I've been close against them but have not yet won. But I'm still working on it."
The German, ranked 71st, broke her Swedish opponent six times in a contest lasting one hour, 49 minutes.
Barrois beat Medina Garrigues in their only previous meeting, on clay at Strasbourg in 2009 when the Spaniard retired after losing the first set.
"I didn't have any special tactics in this win," said Barrois, losing finalist a year ago in Strasbourg to Maria Sharapova.
"I just stayed concentrated on all the points and tried to play steady.
"She's a good clay player and I had to fight for every point."