Mariano Puerta saw off fellow Argentine Guillermo Canas 6-2 3-6 1-6 6-3 6-4 in a gruelling encounter to reach his first Grand Slam semi-final in Paris.
Puerta will face Russia's Nikolay Davydenko in Friday's semi-finals.
Ninth seed Canas looked to have seized control when a run of 10 of 11 games put him two sets to one up.
But Puerta rediscovered the form that saw him sweep through the first set to level the match before a break at 2-2 in the fifth proved decisive.
He now faces Davydenko for a place in Sunday's final against either world number one Roger Federer or Spanish teenager Rafael Nadal.
Russia's Davydenko, seeded 12th, survived a tense battle with Spaniard Tommy Robredo in Wednesday's second quarter-final.
The 23-year-old, like Puerta, reached the last four of a Grand Slam for the first time in his career after a 3-6 6-2 6-2 4-6 6-4 win.
Puerta is playing in his first Grand Slam event since being suspended for nine months in October 2003 after testing positive for a banned substance.
An investigative panel determined that a doctor prescribed the drug to Puerta to treat an acute asthma attack - and the 26-year-old believes the whole experience helped him.
"When you go through a rough period, I'm sure that it just makes you become stronger," he said.
"It's hard for people to sink you. Today, I can tell you, I feel very strong.
"I just don't think back, don't waste my energy remembering things that passed."
Puerta needed three hours and 35 minutes to get the better of friend and compatriot Canas.
"I've never played against such a good defender as Canas," said Puerta.
"He is one the best in the world at that.
"It's very special to be in the semis. When I got to Paris two weeks ago I had the idea I was going to make it to the second week but I can't believe I've reached the semi-final."
Canas insisted he had no regrets - despite letting his lead slip.
"If I had to go back and change something, I think I'd change Puerta," said the ninth seed.
"He played in the important moments better than me, and, for this, he is in the semi-final."
Davydenko, who turns 24 on Thursday, took three hours and 18 minutes to battle past Robredo and admitted fatigue almost got the better of him.
"I was so tired after the match that I had no feeling whatsoever about it," said the Russian, who will move into the world's top 10 after the win.
"The key of the match was that I maybe fought even harder than him.
"I had to battle. I got more and more tired but I tried my best on my last serve and finally it worked."