The spectre of hooligan violence has overshadowed the build-up to the "Superclasico", the biggest club match on the Argentine calendar, when River Plate host Boca Juniors at the Monumental on Sunday.
Despite a government order this season banning away supporters in an effort to curb hooligan violence, there will be 1,000 police officers on duty for fears there could be trouble outside the stadium.
"The priority is that there should be no inconveniences on Sunday. We'll provide technological back-up. Let's not forget there are many who want things to go badly," Security Secretary Sergio Berni told Radio 10 in midweek.
"We're not prepared to take a step back (in dealing) with the violent ones in football."
The ban on away fans was implemented after an Estudiantes supporter was killed in a clash with police at the end of last season and two men died after fighting between rival Boca hooligan factions before an off-season friendly that was then cancelled.
River have been ordered to return the money paid by fans who are not members of the club after the unauthorised sale of 1,700 tickets for one of the stands to all comers, which included Boca supporters as revealed by Fox Sports television.
The home side's coach Ramon Diaz heated up the atmosphere earlier in the week saying he was upset that German Delfino, one of Argentina's most promising younger referees who sent him to the stands for dissent twice last season, would officiate the match.
"He'll send me off after 10 minutes," Diaz, renowned for his sarcastic comments, told reporters.
Boca vice-president Juan Carlos Crespi retorted: "Boca have never questioned referees (performances)."
"We mustn't let the referee and the ambiance affect us," said River Plate midfielder Manuel Lanzini, who scored the fastest goal ever in a superclasico after 43 seconds when the teams drew 1-1 at Boca's Bombonera in June.
The teams' two main strikers, River's Colombian Teo Gutierrez and Emmanuel Gigliotti of Boca, joined their clubs this season and will be playing in their first superclasico.
Gutierrez is approaching his best form after a slow start to the season while Gigliotti gave himself an ideal appetiser with both goals in Boca's 2-0 win over Quilmes last weekend.
Boca have the classier midfield with current Argentina playmaker Fernando Gago and predecessor Juan Roman Riquelme creating the chances.
"It's easy to play with Roman, he puts the ball exactly where you want it and you just have to push it in," Gigliotti told TyC Sports after Sunday's win.
Riquelme said the match would be tough in an all-River atmosphere.
"We're going to face a very determined team and their fans, who are going to demand they take the game to us. They are never satisfied just winning. The true River fan wants the team to play well," he said.
Boca coach Carlos Bianchi will be waiting until the last minute for fitness reports on several first-choice players.
However, former Atletico Madrid centre back Daniel "Cata" Diaz is ready to return from injury as Boca look to go a fourth league match without conceding a goal, while River will be hoping to extend an unbeaten run to five.
Boca are four points behind leaders and title holders Newell's Old Boys in fourth place and River are six adrift in fifth at the halfway stage in the "Inicial", first of two championships in the season.