Puerta and Nadal will play the first all-lefty men's final at Roland Garros in the Open era. Nadal will try to become the first man since Mats Wilander in 1982 to win the French Open in his debut.
Puerta, an Argentine left-hander who has climbed to 37th in the rankings from 440th last August, struggled with his serve but kept Davydenko on the run throughout their 3-hour, 29-minute match. By the fourth set the Russian was occasionally bending over between points, hands on his knees, and he was unable to hold a 4-2 lead in the final set.
Playing in his first major event since serving a nine-month drug suspension, Puerta gives Roland Garros an unseeded men's finalist for the third year in a row. Unseeded Argentine compatriot Gaston Gaudio won the title last year.