Madrid, Nov 5 (IANS): The 13th round of La Liga action sees Barcelona travel to Celta Vigo after an important Champions League win, while Atletico Madrid visit Valencia after losing tamely to Liverpool and Real Madrid face Rayo Vallecano after being booed off by their own fans.

Here are some things to look out for this weekend in Spain:

1. Can erratic Celta upset Barca?

Sergi Barjuan leads Barcelona in Celta Vigo's Balaidos Stadium on Saturday for what will almost certainly be his last game in charge before Xavi Hernandez takes over.

Barca have improved slightly under Sergi, showing more aggression in their play, but the weaknesses that were so obvious under Ronald Koeman still remain, as does a long injury list that includes Sergio Aguero, Pedri, Ousmane Dembele, Sergino Dest, Sergi Roberto and Gerard Pique.

Celta have been erratic this season and their home form has been especially poor, but if players such as Nolito, Iago Aspas and Brais Mendez have a good day, they can still cause Barca a lot of problems on the break - and that appears to be one of Barca's weak points this season, reports Xinhua.

2. Real Madrid need to improve against Rayo

Two goals from Karim Benzema gave Real Madrid a much-needed Champions League win at home to Shakhtar Donetsk on Wednesday night, but Carlo Ancelotti's men were guilty of allowing Shakhtar to stay in the game and were booed off the pitch by some of their fans at the end of the game.

While that may say as much about the expectations of some supporters as it does about the team, Ancelotti needs to inject a bit more life into his side. Eduardo Camavinga could come into midfield, but with Gareth Bale back in training but not yet fully fit, Eden Hazard in apparent exile and Rodrygo injured, it looks as if most of the attacking focus will again fall on Benzema and Vinicius Jr.

3. Which Atletico will we see in the Mestalla?

Atletico Madrid's week began with a convincing win at home to Real Betis, but they followed it up with a 2-0 defeat to Liverpool in which they were very much second best. Now coach Diego Simeone has to take his team to face Valencia, who last week ended a run of seven games without a win as they defeated Villarreal.

Stefan Savic will add some steel to Atletico's defense, while Antoine Griezmann is back after missing out in midweek for what promises to be a no-holds barred match between two sides coached by men whose philosophy is 'win at all costs'.

Don't expect much flowing football and don't be surprised to see a recital of football's dark arts in a must-win game for both sides.

4. A Seville derby with Europe in play

The dark arts are never far below the surface in the Seville derby between Real Betis and Sevilla, which will be played on Sunday night.

The game takes place with Sevilla third in La Liga and Betis sixth, but both sides go into the match off the back of European defeats in midweek.

Seville derbies tend to produce a mix of exciting football, mixed with bad challenges, theatrics and controversy, which usually make them hugely entertaining. Expect more of the same this weekend as both teams need to recover from a tough week, although Sevilla may think their solid defense will be enough to earn them at least a point.