source BBC SPORT
Argentine giants Boca Juniors say they will take nothing for granted when they face Tunisia's Etoile du Sahel in the Club World Cup on Wednesday.
Boca coach Miguel Angel Russo admitted he had been expecting to play Mexico's Pachuca until Etoile surprisingly beat them 1-0 on Sunday.
Boca Juniors will now play the Tunisians in the semi-finals of the tournament of continental champions.
"I myself and the Argentine press had thought all along that Pachuca would be our likely opponents," Russo said.
"In football top favourites have lost many times. We cannot rule out such a possibility here."
The African champions stole the game with an 85th-minute goal through midfielder Moussa Narry, having soaked up waves of Mexican attacks and played on the break.
Boca's Uruguayan midfielder Alvaro Gonzalez said: "Honestly speaking, we have mainly studied Pachuca and just a little about Etoile."
"Etoile had a very effective defence-line," the 23-year-old acknowledged.
"But we are used to fighting defensive sides in Argentina and we have penetrated their backlines and scored goals.
"We are confident to break down the opponents' defence-line," he added.
Boca are widely expected to see off Etoile to reach the final, where they should play Italy's AC Milan, who face the winners of a match between Urawa Reds of Japan and Sepahan of Iran.
Boca and Milan won three times the Intercontinental Cup, a traditional South American-European championship which was merged into the Club World Cup in 2005.