The Argentina international, who last season netted 73 goals in competitions for Barca as he became the club's all-time record scorer, has suffered a calf strain and was not part of the 21-man squad that travelled to Germany for Tuesday evening's friendly.
Barca's medical staff say that Messi's availability for upcoming matches depends on how he responds to treatment.
Tito Vilanova's side are due to face Raja Casablanca in a friendly in Morocco on Saturday before taking on Espanyol in the Catalan Supercup next Tuesday. They then play friendlies against big-spending Paris Saint-Germain and Manchester United on August 4 and 8, respectively.
The USA will wear their blue away jersey against Jamaica in their World Cup qualifier on Friday night.
Support the USA national team with an official 2013 Centennial soccer jersey from Nike. Its Official.
The Nike Hypervenom is the latest cleat silo from Nike. It will change your game and is worn by the game's top players.
England will debut their new away jersey against Brazil at the Maracana Stadium on Sunday. Get in the Gear
Jamaica is in need of a win against the U.S. Get the jersey of the Reggae Boyz.
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
Germany is one of the top teams ever and they will play the US on Sunday.
Neymar's move from Santos to Barcelona is no doubt the biggest summer transfer.
Manchester City will try and win back the Premier League title with this new soccer jersey from Nike!
Barcelona will wear this new home soccer jersey next season. They also have a new away jersey. Get them both.