体坛英语资讯：Copa Libertadores preview: Argentina and Brazil clash in semifinals

RIO DE JANEIRO, Oct. 21 -- Bitter football rivals Brazil and Argentina will this week face off in two tantalizing battles for a place in the final of South American football's top club competition.

On Tuesday, Buenos Aires giants River Plate will host defending champions Gremio of Porto Alegre and on Wednesday Luiz Felipe Scolari's Palmeiras will also visit Argentina's capital for a clash with Boca Juniors in their Copa Libertadores semifinal first legs.

Return matches in Porto Alegre and Sao Paulo will be played the following week, with the winners over both legs earning a berth in the final, also to be played on a home-and-away basis on November 11 and 28.

River Plate and Gremio both have injury worries as they prepare for Tuesday's clash at the Monumental in Buenos Aires' northern districts.

The Argentine outfit received good news on the weekend when medical staff declared that midfielder Gonzalo Martinez has fully recovered from a hamstring strain.

However doubts hang over the availability of Argentina international goalkeeper Franco Armani, who has not played since suffering a quadriceps injury in early October.

"He has been feeling better these last few days but needs more time to fully recover," River coach Marcelo Gallardo said on Sunday. "I think he will be okay but we'll see in the next few days."

Gremio's fitness concerns are more pressing. Forwards Luan and Everton, the team's leading scorers this year, have both been ruled out of Tuesday's match by coach Renato Gaucho despite local media reports suggesting they could play.

Luan is nursing a foot injury while Everton is struggling to recover from a thigh problem that forced him out of Brazil's international friendlies against Saudi Arabia and Argentina earlier this month.

Gremio could also be without veteran right-back Leo Moura, who has a calf complaint.

Wednesday's clash at the Bombonera features two teams that have had vastly different fortunes in the Copa Libertadores.

Palmeiras, the most successful club in Brazil's Serie A history with nine titles, have won just one Copa Libertadores title: in 1999 during Scolari's first spell as coach. They were losing finalists to Boca Juniors the following year but have mostly struggled in the competition since then.

Boca, meanwhile, are six-time Copa Libertadores champions and could this year equal Independiente's record as the club with the most titles.

Palmeiras have been rejuvenated under Scolari, who returned to coach the club for a third time in late July. Since then the Sao Paulo outfit have won 16 and lost just two of their 23 matches in all competitions and they currently hold a four-point buffer at the top of Brazil's Serie A standings.

Conversely, Boca have struggled to recapture the form that saw them win the past two Superliga Argentina titles. Guillermo Barros Schelotto's men are currently fifth in the Superliga standings with just four wins from nine matches this season.?