Buenos Aires, Oct 24 (IANS): Gremio achieved a valuable 1-0 win over River Plate at the El Monumental Stadium here in the first leg of the semi-finals of the Copa Libertadores football tournament, thanks to defender Michel, who headed home the only goal of the match.

The reigning tournament champions took to the pitch determined to stop River Plate in midfield here on Tuesday, reports Efe news agency.

During the first half, River Plate attacked mainly on their left flank and Milton Casco, the full-back on that side, at times looked more like a midfielder than a defender.

At the beginning of the second half, River Plate's Jonatan Maidana tried a header from a corner and came close to scoring the long-awaited goal.

In the 61st minute the only goal of the game finally came from Michel's header.

Gremio gained confidence and remained faithful to their plan: battling in the center of the field to recover the ball and go fast on counterattack.

River Plate tried but again and again against hit an impenetrable defensive wall.

Marcelo Gallardo quickly made changes in search of solutions, but his attempt was in vain.

The second leg will be played on October 30 at the Arena do Gremio in Porto Alegre.