Real Madrid took a significant step towards a first La Liga title in five years with a convincing 3-0 win over local rivals Atletico Madrid thanks to Cristiano Ronaldo's hat-trick.
AFP Sports looks at five things we learned from week 12 in La Liga.
Injuries force Real change for good
Real's first Madrid derby league win in four seasons was even more impressive given the absence of six key players with injury.
With strikers Alvaro Morata and Karim Benzema missing, coach Zinedine Zidane was forced into playing Ronaldo in a more central role.
Gareth Bale and Isco also shone in their more natural positions on the left and behind Ronaldo respectively as a much more balanced Real produced their best display of the season.
The key for Zidane is to now maintain that balance when some of his big names return to fitness in the coming weeks.
Atletico's defensive wall collapses
Atletico's third defeat in four league games looks to put an early end to their title ambitions as Diego Simeone's men trail Real by nine points and slipped down to sixth.
Simeone's success at Atletico has been built on a rock-solid defence, but in aiming to introduce more of an attacking edge to their play this season, that solidity has been lost.
For the first time in Simeone's reign, Atletico have conceded in five consecutive league games and Saturday's defeat was the first time since September 2012 Los Rojiblancos had conceded three goals at home in La Liga.
Unhealthy dependence on Messi returns
By uniting Messi with Luis Suarez and Neymar, Barca had hoped to not only arm themselves with the most feared forward line in the world, but also ensure an end to what the Spanish press christened Messi-dependence during Pep Guardiola's reign in charge.
Without the injured Messi for two months last season, Neymar and Suarez ensured Barca gained rather than lost ground in the title race.
However, in all four of the 12 La Liga games Barca have failed to win this season, they have paid a heavy price for Messi not completing the 90 minutes.
The Argentine also missed a 4-3 defeat to Celta Vigo last month, limped off injured in a 1-1 draw with Atletico and couldn't turn around a shock 2-1 loss at home to Alaves in September after being left on the bench due to his commitments with Argentina.
Things could get even worse for Barca ahead of El Clasico in two weeks' time as they travel to a soaring Real Sociedad next weekend.
Sociedad have been Barca's bogey team in recent seasons, winning all of their last three meetings at home.
A comfortable 3-1 win at Sporting Gijon was Sociedad's fourth victory in a row to lift them above Atletico into fifth and just a point off the top four.
Eibar 100 not out
La Liga's loveable Basque minnows continued their brilliant early season form with a 1-0 win over Celta Vigo to move up to eighth.
Fran Rico's winner was Eibar's 100th La Liga goal in just their third season in the top flight.
And having already amassed a nine-point lead over the bottom three, a fourth La Liga campaign is already looking assured.