Messi is set to miss the rest of the season after tests revealed the extent of the damage to his right hamstring.
He underwent a scan on Tuesday with a Barca statement revealing the results.
It read: "Tests this Tuesday morning showed that Leo Messi has an elongation in the femoral biceps in his right leg. The expected absence is two to three weeks.
"How the injury evolves will determine the player's availability for future games."
Messi started Sunday's win at Atletico Madrid but limped off after 67 minutes after experiencing further problems with the injury.