Madrid (Spain), Nov 12 (IANS): The majority of Spain's La Liga clubs make their debut in the Copa del Rey knockout tournament this weekend, although at first view there don't appear to be many chances of a 'giant-killing' act.

Real Madrid, FC Barcelona, Valencia, and Cup holders Betis are all exempt from this and the next round as they will play the Super Cup in Saudi Arabia in January, but sides such as Atletico Madrid, Real Sociedad and Athletic Club Bilbao are all in action.

The complicated system for the draw in Spain means that 10 top-flight sides will meet teams from the 'Preferente' category, which is effectively the sixth tier of the Spanish game.

The difference in skill and fitness means that sides such as Osasuna, Valladolid, Mallorca and even Elche, who have yet to win a league match this season, should have few problems in moving into the next round even if their respective coaches give them a chance to their fringe players, reports Xinhua.

Atletico Madrid have a slightly more difficult task as they visit Almazan, who play in the fifth-tier league. Atletico have suffered a dip in form and coach Diego Simeone can't afford any errors, especially after recent disappointments in the competition.

Athletic Club Bilbao visit Alzira, who are currently 16th in their group of the RFEF Second Division (fourth tier) and that is the sort of game where Athletic has everything to lose and little to gain, especially with coach Ernesto Valverde likely to rest any players going to the World Cup.

Perhaps the best chance for an upset is in the north of Spain, where Real Union, from Irun, hosts Cadiz. Although they are bottom of the RFEF First Division, Real Union is the highest-ranked side to play a top-flight club and Cadiz won't be happy about having to make the long trip for the game.

Finally, Arenteiro, from the RFEF Third Division, entertain Almeria after taking Valencia to extra time on their muddy pitch a year ago.