A day after knocking off fellow Russian Yevgeny Kafelnikov, Davydenko beat seventh seed Max Mirnyi of Belarus, 6-4, 3-6, 6-3 Saturday in the semifinals.
The 22-year-old Davydenko will get a chance at a second title just three months after starting the season with a trophy on hardcourt in Adelaide.
"I'm so happy to reach another final. It's my first on clay and it's good for my game," Davydenko said. "I hope to reach the Top 50 and then start getting into the Masters Series events. I found out in Australia that I can play well. I hope this won't be my last final."
Calleri ousted No. 5 Tommy Robredo of Spain, 6-4, 6-2, Saturday in the semifinals.
Argentina has a chance for back-to-back titles at the Estadio Nacional after David Nalbandian won the event in 2002.
"Conditions were tough," said Calleri. "There was a lot of wind. The balls were flying around. I managed to play a good match, but it was not as easy as the score indicates. Technically, I was very strong, that's why I managed to win."
Davydenko and Mirnyi split the first two sets before the Russian won the first four games of the third. Mirnyi fought back for one break, but Davydenko saved three break points in the final game to serve out the victory in the first meeting between the pair.
"It's tough to play Max on any surface, he doesn't play my game," said Davydenko. "I just tried to stay error-free."
On the women's side of the draw, German Julia Schruff will play Magui Serna of Spain in the final on Sunday.
Schruff, the 20-year-old daughter of a tennis instructor, defeated Switzerland's Emmanuelle Gagliardi 6-3, 6-4 Saturday and now has a chance to play for a title in only her fourth tournament at the top level.
"I can't believe I'm in the final," said Schruff, whose previous best came in the semifinals of a $25,000 challenger in Cairo last November. "I have no words for this, I don't know how I did it."
Schruff beat top seed Katarina Srebotnik in the second round, then knocked off Ludmila Cervanova in the quarterfinals.
Serna crushed third seed Virginie Razzano of France, 6-0, 6-1 on Saturday in a match delayed two hours due to rain.