Who'd have thought Barcelona would suffer their first defeat of the season to a side from the Dutch Eredivisie?
So it has proved, as they went down 2-1 at Ajax on Matchday 5. It's not like they needed a wake-up call, but it does go to show that Barca aren't totally invincible.
Domestically, however, they don't seem to be too affected, dropping just two points all season, and winning their last five games in La Liga, scoring 14 and conceding twice.
In the absence of the injured Lionel Messi, young talents like Neymar, Alexis Sanchez and Pedro are stepping up, and it's great to see Cesc Fabregas now well and truly cemented in Tata Martino's starting line-up.
Athletic Bilbao are their opponents this weekend, a team who haven't beaten them since 2006, and even then it was a hollow victory: Barca had already clinched the league title and the match at the Estadio San Mames came three days after their Champions League final triumph over Arsenal in Paris.
Not that Barcelona are the only side who are scoring for fun - Atletico Madrid, in second, smashed seven past Getafe, five of those coming after the break.
And again, it's not just about one man: Diego Costa's strike-rate is impressive enough, but now it's been supplemented by the goals of David Villa and Raul Garcia.
Indeed Real Madrid have even responded superbly to their defeat in El Clasico - 20 goals netted in four straight wins. With every passing week, Gareth Bale is looking more the "galactico" and Cristiano Ronaldo more the Ballon d'Or winner that he should become in January, if sense ultimately prevails.
The title race is still very much alive between those three, but after Villarreal and Bilbao, no-one else is safe from relegation. Eight points cover Real Sociedad in sixth down to second-bottom Rayo Vallecano.
One of the biggest shocks of the season is Real Betis, propping up the table. Last weekend's 4-0 thrashing by Sevilla in a local derby must have hurt, and although coach Pepe Mel has backing at board level, the rot has to be stopped, and sharpish too.
We have new leaders in Serie A, with Juventus hitting a purple patch of five successive league victories to overhaul still-unbeaten Roma.
Rudi Garcia's side may live to regret those draws against very beatable sides in Torino, Sassuolo and Cagliari, and now that Juve have just the narrowest of leads, you can imagine they won't relinquish it easily, as they go for their 30th Scudetto.
Part of Antonio Conte's success has been down to the evergreen Andrea Pirlo, but partly also the indefatigable Paul Pogba and Carlos Tevez.
Fernando Llorente is starting to chip in with goals too - on top of that, their defence has been supremely stubborn, only breached by Real Madrid during the last month. Juve are at home to Udinese this weekend, while Roma go to Atalanta
Napoli now also need to show their character - back-to-back league defeats mean that they're playing catch-up, and now Rafa Benitez's boys face Lazio away. Their boss Vladimir Petkovic is under pressure too - and not just because capital rivals Roma have almost double their points tally.
The biggest story in Italy, though, is the mess that is AC Milan - they may be on the brink of the Champions League knockout stages, but they've gone winless in five league games for the first time since 2007.
Mario Balotelli's form has disappeared domestically with no goal in two months, not even from the penalty spot: a truly pathetic effort against Genoa from 12 yards out last weekend meant Milan drew that game 1-1, prompting an angry reaction from the club's fans. Kaka and Christian Abbiati had to appease them, and Kevin Constant had to delete his Twitter account because of the abuse.
Behind the scenes, the tensions of the San Siro boardroom struggle principally involving owner Silvio Berlusconi's daughter Barbara, a club director, and vice-president Adriano Galliani, seem to be taking their toll on head coach Massimiliano Allegri. Publicly, the club are offering him their support, but surely if the Rossoneri's form doesn't improve, he can't last past Christmas.
Der Klassiker could have turned out so differently if Borussia Dortmund had taken their chances, but Bayern Munich made them pay for their profligacy after half-time and waltzed to a 3-0 victory.
It's hard to see where the Bundesliga champions will drop points this season, having already travelled to Dortmund, Leverkusen and Schalke. On top of that, Pep Guardiola now has Mario Gotze and Thiago Alcantara back after injury, so whispers of a potential unbeaten league campaign have already begun to go around.
Dortmund, however, are winless in three domestically, and an injury crisis has started to hit hard: Neven Subotic is out for the season, Mats Hummels until the New Year and Marcel Schmelzer for another couple of weeks.
Should Mainz expose Jurgen Klopp's weakened defence this weekend, then surely hopes of a ninth Bundesliga title would evaporate completely, especially with Bayern taking on bottom side Eintracht Braunschweig and second-placed Bayer Leverkusen facing winless Nurnberg.
In Ligue 1, Paris Saint-Germain now lead by four points and are still undefeated. Swedish striker Zlatan Ibrahimovic may not be going to the World Cup, but he continues to take his frustrations out on PSG's opponents in France's top division.
Lyon are the visitors to the Parc des Princes this weekend - a significant step up in quality for Remi Garde's side, after decent victories over Guingamp and St Etienne to get their season back on track.
PSG's nearest challengers are now Lille, with Rene Girard using the same formula for success as he had at Montpellier two seasons ago, based on a robust defence.
In fact, that's putting it mildly; Lille haven't conceded in 855 minutes in Ligue 1, and it could be 10 clean sheets in a row this weekend at Valenciennes. One of the previous nine was against Monaco, and the pressure building on Claudio Ranieri was only slightly alleviated by their 1-0 win at Nantes.
Like in Italy, France's bottom three all have different coaches to the ones who started the season, which has meant Fabrizio Ravanelli has sadly departed Ajaccio.
The former Middlesbrough striker did impress with his work ethic during his time in charge on the island of Corsica, and he'll surely be back in management soon.
Still, lower-to-mid-table clubs should take that as a warning - with Christmas around the corner, chairmen and owners often make changes ahead of the January transfer window to give the new man a chance to shape the squad with signings. December is clearly not the month to lose form, because patience will be in short supply.