“I wanted to get started and unfortunately I had a mishap during the first training session which will keep me out of action for a while,” the five-time Ballon d’Or winner posted on Instagram.
The Argentina star has already been ruled out of the team’s trip to Florida for a one-off friendly against Napoli in Miami on Wednesday.
“Tests carried out have diagnosed a grade 1 calf strain,” the Spanish champions said in a statement, an injury that can require around two weeks of recuperation.
“Messi will remain in Barcelona and will now not travel to the USA for the club’s tour. His availability to come back to action will be dictated by his recovery from the injury.”
Messi, who was at the Camp Nou on Sunday for the squad presentation ahead of the match against Arsenal, said he was sorry to be missing the Florida trip.
“I wanted to be with the team and with the people who follow us in the US,” said Messi.
“This time it will not be possible but we will meet again soon. I kiss you all.”
The club open the new La Liga campaign at Athletic Bilbao on August 16.