Madrid,  The new La Liga season kicks off this weekend after a subdued summer in the transfer market in terms of arrivals, and with Leo Messi leaving FC Barcelona. Here are some things to look out for as the ball gets rolling again in Spain.

1. What will happen at Camp Nou?

FC Barcelona kick off the post-Messi era with a home game against Real Sociedad and with just over 20,000 fans back in the stands and while the players will no doubt be glad not to play in front of empty stands, at the club, there must be some worries about the reaction to Messi's departure. Barca fans are in a state somewhere between shock, disbelief and anger that financial fair play rules led to Messi's 'adios' and Barca president, Joan Laporta can expect an uncomfortable evening - especially if things don't go Barca's way on the pitch.

There are still doubts over whether or not Barca's summer signings, Memphis Depay and Eric Garcia will be able to play and with Frenkie de Jong, Kun Aguero, Ansu Fati and Oscar Mingueza all injured, it already looks like a difficult start to the new campaign for coach Ronald Koeman, who desperately needs to start with a win, reports Xinhua.

2. Bale back for Real Madrid?

A year ago Gareth Bale joined Tottenham on loan with his relationship with former Real Madrid coach Zinedine Zidane virtually non-existent and with the fans and press questioning his attitude after a string of injuries. The return of Carlo Ancelotti looks to have brought Bale back into the fold and he is in line to start as they kick off the new campaign away to Alaves.

Real Madrid also lost two key players with Sergio Ramos also joining PSG and Raphael Varane moving to Manchester United and although David Alaba is a fine replacement, the pressure will be on Eder Militao in the back four.

There are still doubts over Ancelotti's squad, although Isco (like Bale) also seems to be back in contention and the side the Italian fields against Alaves will show which players could leave before the end of the month.

3. Tough opener for Atletico Madrid

Atletico Madrid begin their title defense away to Celta Vigo in what promises to be an interesting game. Celta developed an intense attacking style of football last season under coach Eduardo Coudet and with players such as Iago Aspas, Brais Mendez, Santi Mina and Denis Suarez, they should compete for a place in Europe this time around.

Things have been reasonably quiet on the transfer front for Atletico (like most of Spain) and although the arrival of Rodrigo de Paul should give them more goals from midfield, the plan will be much the same as last season.

With Marcos Llorente and De Paul providing drive from midfield and Suarez still in attack, this promises to be a game that could be more open than Diego Simeone would like, but one which will entertain neutral fans.

4. How will the new teams perform?

It's always interesting to see how sides promoted to the top-flight perform in the opening weeks, although Mallorca and Espanyol have bounced back after just a season in the second division and should be reasonably well equipped for life back in the elite.

Espanyol have Raul de Tomas to score their goals and Wu Lei looking to show his worth as they travel to play Osasuna, while Mallorca, who entertain Betis, have got Take Kubo back on loan from Real Madrid and have a good coach in Luis Garcia.

Rayo Vallecano look to have the weakest squad of the promoted sides, but forward Martin Merquelanz is a good loan signing and he reunites with coach Andoni Iraola after they worked together at Mirandes. Iraola is one of Spain's most promising young coaches, but his team face a tough debut against Sevilla.