MADRID, Sept. 29 (Xinhua) -- There is a new leader in La Liga after FC Barcelona beat Real Sociedad and Atletico Madrid thumped Real Madrid in Saturday's derby. Here are some things we learned in Spain this weekend.

1. The Lamine Yamal effect

There are no more secrets about Lamine Yamal is capable of doing on a football pitch after over a season as a regular for Barcelona.

The 18-year-old hadn't played since picking up a pelvic problem with the Spanish national team, but returned after missing four matches with the score tied 1-1 at home against Real Sociedad on Sunday night.

He needed just a minute to produce a trademark turn and run before crossing for Robert Lewandowski to head in the winning goal, showing just how important he is for club and country.

The problem now will be if Spain coach Luis de la Fuente calls him into his next squad, knowing that if Yamal is overplayed, he could suffer further problems.

2. Alvarez ends decisive week for Atletico in derby win

It's been an incredible week for Julian Alvarez, who just over a week ago was seen lamenting the fact he had been subbed out of his side's draw in Mallorca.

He responded with a hat-trick in a fightback at home to Rayo Vallecano and then scored a penalty and a free-kick to put Atletico 4-2 up against Real Madrid in Saturday's derby.

Atletico showed personality to come back from 2-1 down to its neighbor and then dominated the second half, with the aggressive and intense football that had been missing in the first month of the campaign.

The 5-2 win puts Atletico back in the title fight, but with a seven-point gap to close on Barcelona, Simeone's side can't rest on their laurels.

3. Questions to answer for Real Madrid

Saturday's defeat ended Real Madrid's 100 percent start to the season, but also raises some questions about that start given that Real Madrid has so far beaten Osasuna, Oviedo, Mallorca, Real Sociedad, Levante and Espanyol.

Of those six rivals, only Espanyol is in the top-half of the table - and traditionally struggles in the Bernabeu, while Levante and Oviedo are recently promoted, Osasuna sits 13th and Real Sociedad 17th after difficult starts to the campaign.

So, the question is: How good is Xabi Alonso's side?

Perhaps next Saturday's game against third place Villarreal will give us some answers.

4. Elche enjoys dream start to top-flight

Not even Elche coach Eder Sarabia would have predicted that his side would be unbeaten and fourth in La Liga after seven matches this season, but the recently promoted outfit is sitting behind Barca, Real Madrid and Villarreal in the classification after a 2-1 win at home over Celta Vigo on Sunday.

Elche completely outplayed the side that finished seventh in La Liga last season, creating 17 chances and enjoying 62 percent of the ball.

Sarabia's team is happy on the ball and also willing to hit long passes to twin strikers Andre Silva and Rafa Mir and so far the combination of tactics is working very well. ■