MADRID, Jan 1 (Reuters) - Unfancied Zamora will score the biggest upset of the Spanish season if they manage to halt Barcelona's 13-match winning streak when they host the Catalans in the first leg of their King's Cup tie on Tuesday.
The odds are stacked against the humble third-division side who are the only non-Primera Liga team to have made it into the last 16 of this year's competition.
While Zamora have had to negotiate their way through three rounds to get this far, Barca and the eight other Primera Liga sides who have been involved in any sort of European competition this season were given automatic byes into the last 16.
To make the task even more difficult for Zamora, the ties are now played over two legs and the Castilians have to play the return at the Nou Camp in a week's time.
Zamora have been given a glimmer of hope, however, because the Catalans will be without several of their most influential figures for the first leg and have a poor record in the domestic knockout competition in recent seasons.
Barca's prolific attacking trio of Samuel Eto'o, Ronaldinho and Lionel Messi have all been left out of the squad for the trip to the Ruta del Plata stadium, and winger Santiago Ezquerro is favourite to lead a makeshift frontline.
Last season Frank Rijkaard's side were knocked out of the Cup by third division Gramenet. With Barca's attention on retaining their Primera Liga crown and making further progress in the Champions League, Zamora will hope to catch their opponents off guard.
Barca keeper Victor Valdes insists there is no chance of the Catalans taking their eye off the ball, however.
'These are the sort of games where there is potential for an upset,' Valdes told a news conference this week.
'We haven't done well in this competition in recent years and we have to show the same respect for Zamora as for a first division side.'
On paper, arch-rivals Real Madrid have a much tougher tie with a trip to the Basque Country to meet Athletic Bilbao on Tuesday.
The nine-times European champions will be glad to see the back of a year which ended with the dismissal of coach Vanderlei Luxemburgo and the resignation of director of football Arrigo Sacchi.
Things have gone little better under new boss Juan Ramon Lopez Caro, however, and the team were dealt a further blow when leading striker Ronaldo suffered yet another injury in the first training session after the Christmas break.
Reserve team striker Roberto Soldado, who has performed well every time he has stepped into the Brazilian's shoes this season, will be given another chance to prove his worth in the first leg at San Mames.
With an 11-point deficit to make up on Barcelona in the league and a daunting task if they are to win through the knockout rounds of the Champions League, the Cup may well provide Real's best hope of winning a trophy this season.
Opponents Athletic appear to have turned the corner since Javier Clemente took charge in November but with only goal difference separating them from the relegation zone their main priority is securing their survival in the top flight.
The remaining first-leg matches are to be played on Wednesday.
Holders Real Betis are hoping that new recruits Roberto and Diego Tardelli will be able to give them a hand when they travel to high-flying Celta Vigo.
The tie between a rejuvenated Deportivo Coruna and last season's losing finalists Osasuna and the regional derby involving Villarreal and Valencia also promise to be tightly contested affairs.