Real Madrid were surprisingly beaten at home by Real Betis on Wednesday night, with Antonio Sanabria's injury time winner meaning Zinedine Zidane's team find themselves in eighth place in the La Liga table.
Barcelona had no such troubles this week as they brushed Eibar aside 6-1 at Camp Nou on Tuesday, and lead the table by two points from Sevilla.
It's early days though, and whilst Real have only won two of their five league matches so far, Spain's big two are still the top two in the betting.
All was not well at the Camp Nou over the summer. Losing Neymar to Paris Saint-Germain was a major blow to Barca's title aspirations and the prices reflected that, with Madrid kicking off the campaign as odds on favourites to retain their crown.
On 27th August, Madrid were cut to around 8/13 (1.62) to win the league, and Barcelona were out at 6/4 (2.50). Three games later, and those prices have essentially reversed. The champions can now be backed at 6/4 (2.50), with their Catalan rivals available at 6/10 (1.60), that despite the injury to Ousmane Dembele, who will be sidelined for several months.
The switch in prices has obviously been down to the results in the intervening period. Barcelona returned from the first international break of the season by winning 5-0 in their derby with Espanyol. Earlier that day, Real had only drawn 1-1 at home with Levante, having had to come from behind to do so. Los Blancos struggled against Valencia too, needing a late equaliser to salvage a point.
Both sides then won last weekend. Zidane's team won reasonably comfortably at Real Sociedad, but there was far more drama for their great rivals. Barcelona left it late to win 2-1 at Getafe, in the kind of result which is the hallmark of champions.
Whenever one of the two giants fails to win the prices will no doubt shift again. The first El Clasico of the season is not until two days before Christmas and there are sure to be plenty of twists and turns between now and then.