5 key talking points ahead of Atletico Madrid v Barcelona

Barcelona have a 100 per cent record after seven games, but Atletico are also unbeaten with four wins and three draws.

Here, Press Association Sport takes a look at some talking points ahead of the meeting between the first and fourth-placed sides in LaLiga.

POLITICAL TENSION REMAINS

This is Barcelona's first game in the Spanish capital following Catalonia's unilateral referendum on independence. Barca's last match against Las Palmas on October 1, the day of the referendum, was played behind closed doors amid unrest in Catalonia. And Gerard Pique, who said people should be allowed to decide the future of the region, was abused by fans while on international duty with Spain. There has been no getting away from the politics with some Atletico fans calling for the Wanda Metropolitano to be filled with Spanish flags on a night when few Barcelona supporters are expected to attend. But Atletico president Enrique Cerezo has tried to diffuse the situation by saying he expects "a football game, not a political demonstration."

MAGICAL MESSI IS ON FIRE

There was no stopping Lionel Messi on Wednesday as his brilliant hat-trick fired Argentina into the World Cup finals. But will Messi suffer from playing at high altitude in the Ecuadorian capital Quito, as well as the effects of jet-lag after his long journey back from South America? Messi could be forgiven for feeling some tiredness as he has played every minute for Barcelona this season, but 11 goals in seven games suggests that he is taking that in his stride. Atletico will also be wary of Messi's incredible scoring record against them - 27 goals in 34 games making the Rojiblancos one of his favourite opponents.

SIMEONE CHASES FIRST

Atletico boss Diego Simeone will certainly be hoping that the Wanda Metropolitano brings a change of fortune for him in this fixture. Despite all of the Argentinian's success at Atletico since being appointed in December 2011, Simeone is still waiting for his first LaLiga victory over Barcelona. In fact, Simeone has won only two of 21 games as the Catalans have dominated the fixture. Those two Atletico wins came in the Champions League, securing progress in the knock-out stage on each occasion in the 2013/14 and 2015/16 seasons. Of the 11 league games played against Simeone's Atletico, Barcelona have won eight - and another victory would put them nine points clear of their rivals.

CAN BARCA BE BREACHED?

As well as averaging more than three goals per game in LaLiga, Barcelona have proved just as effective at the other end of the pitch. Barca's defence has been superb so far this season, conceding only two goals in LaLiga and none at all in the Champions League. Samuel Umtiti has become a force in his second year at the club and established a commanding centre-back partnership with the experienced Pique. So much so that Marc-Andre ter Stegen has made only 12 saves this season. Atletico forwards Antoine Griezmann, Angel Correa and Yannick Ferreira-Carrasco - who have eight goals between them - will need to be on top form to trouble a well-drilled Barca defence.

PAIN IN THE GRASS

Barcelona have had little to be upset about this season, but the length of the grass at Getafe's Coliseum Alfonso Perez did get the Blaugrana's blood boiling. Barca felt Getafe had let the grass grow longer than usual, thereby disrupting their natural passing game. If that was indeed the case, it almost worked for Getafe as Barcelona had to rely on Paulinho's late goal to maintain their winning run. The topic was raised before their trip to Madrid and it remains to be seen whether the Atletico ground staff have had a day or two off in the build-up to the game. But Simeone was not entertaining the subject at his pre-match press conference, saying: "I am not a gardener, I am a coach, and I go to the pitch to prepare the team."