The one fixture that doesn't need any extra build up has found itself all over the world's sports pages, after a linesman went to the anti-corruption authorities to advise he had been told by the proposed match official that decisions should 'favour Real Madrid'.
There has, predictably, been uproar at the highest levels with La Liga, the RFEF and Real Madrid all distancing themselves from such claims.
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It would be newsworthy under normal circumstances, but what gives this claim added credence is Diego Simeone's comments before the start of the season.
The Atletico Madrid manager told AS, via Mark Doyle of Goal.com:
"Dangerously complicated for any team other than Real Madrid [to win La Liga] because it can't happen that Real Madrid wins only one league after seven years.
"So, I see [the Liga title race] dangerously prepared for Real Madrid, sadly."
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Highly likely now that the Argentinian might be asked to explain his comments further.
What's certain is that Barcelona will demand that the most recent claims are investigated fully before the match takes place and indeed that the officials are fully vetted and approved by both sides before the start of play.
It's a row that threatens to overshadow the build-up to what could be one of the most important Clasico's of recent times.
Despite having lost twice already, the Catalans are still on the same points as unbeaten Real at the top of the table. If the status quo remains the same until their match-up, then three points will elevate the winners to sole leaders in the league.
There are a couple of fixtures to negotiate between then and now but, with respect to their opponents, both Barca and Real are playing well enough to continue setting the pace.
Corruption in Spanish football is nothing new of course.
Even as far back as 1943, when Real won by a landslide 11-1 in the second leg of the Copa del Generalisimo, suggestions of an anti-Barca campaign have been prevalent. Interestingly, given that they were the comprehensive losers in that tie, Barca are the ones who continue to speak about it whilst Real prefer to keep quiet on the subject.
A little strange, don't you think?
There is no doubt that La Liga as a brand has been tarnished by this recent episode, but their attempt to sweep things under the carpet could well rebound on them too.
Despite having the best footballers on the planet all plying their trade within their shores, the Spanish football governing body remain sorely lacking in a number of areas.
The fact no one is surprised by these recent developments is worrying indeed.
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