Barcelona had two players sent off but still overcame Santos to advance to the semi-finals of the Copa Libertadores, where they will meet Gremio.

Goalscorer Jonatan Alvez and Gabriel Marques both saw red in the second half as nine-man Barcelona claimed Wednesday's second leg 1-0 to progress 2-1 on aggregate.

It was all to play for in Sao Paulo midweek after Santos left Ecuador with a 1-1 draw and a priceless away goal last week.

However, Santos were unable to build on their positive result away from home as two-time Libertadores runners-up Barcelona secured a final-four berth thanks to Alvez.

Alvez headed home powerfully in the 68th minute after meeting Erick Castillo's inch-perfect cross at the near post.

The Uruguayan was sent off two minutes later but Barcelona managed to advance, despite another red card to Marques, who joined Santos' Bruno Henrique down the tunnel in the 89th minute.

Standing in the way of Barcelona and a spot in the final are Gremio, who prevailed 1-0 against fellow Brazilian outfit Botafogo.

Lucas Barrios' 63rd-minute strike on Wednesday was all that separated the teams over two legs in the quarter-final tie.

The former Borussia Dortmund star headed past Paraguayan counterpart and Botafogo goalkeeper Roberto Fernandez to send Gremio through.

The first leg of the semi-final will take place in October.