Barcelona will be looking to record just their second La Liga win of the season when they welcome Valencia to Camp Nou on Saturday night.
The Spanish champions are currently eighth in the table on four points, while Valencia, who have just appointed Albert Celades as their new head coach, have the same record after three games.
Messi will again miss out against Valencia; Luis Suarez trained on Thursday, though, and should return to the starting XI this weekend in what would be a huge boost to their chances. It is still early in the season, but Barca cannot really afford to drop more points when considering Atletico Madrid's form at the summit.
Atletico are La Liga's only 100% team this season with nine points, while Athletic Bilbao, Sevilla and Levante make up the top four, with Real Madrid in fifth on five points. It is difficult to get carried away with the table at this stage of the campaign, but Barca could fall eight points off Atletico this weekend.
Both of the league meetings between the two teams last season finished level, while, as mentioned, Valencia beat Barca in the Copa del Rey final at the end of May.
Despite a turbulent start to the season, there is no question that the visitors can cause some serious damage at Camp Nou on Saturday night. Barca, who have made their worst start to a campaign since 2008, are expected to welcome Luis Suarez back into the XI, but Messi's absence is a big one when considering that the Argentine has scored his team's last four goals against Valencia. Osasuna and Bilbao have shown the way in terms of harming Valverde's side this term, and Los Che will be looking to do the same as they enter a new era.
As mentioned, Messi will again miss out for Barca due to a calf problem. Luis Suarez is fit after recovering from a calf injury of his own, though, and should start in the final third of the field.
Dembele and Samuel Umtiti are out with hamstring and foot problems respectively, but Valverde otherwise has a strong squad to choose from.
Perez scored against Betis at Camp Nou last time out before providing both assists against Osasuna ahead the international break, suggesting that the youngster could keep his spot in the final third. Ivan Rakitic could also come into the XI having remained at the club despite the widespread speculation surrounding his future. Arthur and Arturo Vidal are also options in that area of the field, though, with Valverde having a whole host of central midfielders to choose from.
There are not expected to be any alterations further back, though, with right-back Nelson Semedo available despite concerns over his fitness earlier in the week.
As for Valencia, it would be a surprise if Celades made major changes from the team that started the 2-0 win over Mallorca before the international break.
As a result, Kevin Gameiro and Rodrigo Moreno should again start in the final third of the field, leaving summer arrival Maxi Gomez on the bench.
Dani Parejo will captain the team from the middle of the park, while former Arsenal youngster Francis Coquelin should also retain his spot. Carlos Soler and Cristiano Piccini are both still on the sidelines for Los Che, though.