Alex scored the only goal as Brazil's Internacional claimed a crucial away win over Argentina's Estudiantes in the first leg of the Copa Sudamericana final despite playing with 10 men for over an hour in La Plata.

The visitors suffered an early blow when midfielder Pablo Guinazu was sent off after only 24 minutes.

But just 10 minutes later Alex converted from the penalty spot after Leandro Desabato had upended Nilmar to hand Internacional the advantage ahead of the return leg in Porto Alegre next Wednesday.

"The match became very difficult for us after the red card. We are exhausted but we had the right attitude and claimed a crucial win," said Internacional's Argentinian playmaker Andres D'Alessandro.

"It's very exciting to play in Argentina against Argentinian sides. It's very hard to live outside the country and therefore this kind of game has a special meaning for me."

The defeat ended an unbeaten run of 43 home matches for Estudiantes, stretching back to May 2007.

"It was one of those nights in which nothing went right. It was a strange game," said Estudiantes midfielder Juan Sebastian Veron.

"We controlled the ball for the entire game and always looked like we would win, but they defended well.

"But nothing is decided yet, we still have 90 minutes to change history. We will travel to Porto Alegre and we will do our best."

Internacional made a strong start but failed to test Estudiantes goalkeeper Mariano Andujar early on as Nilmar was unable to connect with Alex's cross.

The home side responded as Internacional goalkeeper Lauro had to turn away Veron's free-kick and a header from Agustin Alayes.

The game appeared to swing Estudiantes' way midway through the first half as Guinazu picked up a second yellow card for a foul on Veron.

But the Brazilian side were ahead before the break as Alex held his nerve from the spot.

Internacional almost doubled the lead two minutes later as D'Alessandro crashed a free-kick against Andujar's left post.

Estudiantes coach Leonardo Astrada attempted to inspire his side by introducing strikers Jose Luis Calderon and Gaston Fernandez, but the home side failed to test Lauro.

Internacional had a chance to extend their lead in the closing stages but Magrao's volley was well saved by Andujar.

"We played very well. I'm especially happy after having another good performance in Argentina, like I did in the quarter-finals against Boca," said Internacional goalkeeper Lauro.

"But nothing is decided yet and we still have a very difficult match in Porto Alegre."