After leaving the match against Las Palmas on Saturday with a lower leg injury, the Barcelona superstar was immediately taken to a hospital for further testing on his left knee, according to reports.
This is Messi's first serious injury to his knee, and while we shouldn't speculate at this point, it's always worrying to see a player with a knee injury. Messi joins Claudio Bravo, Thomas Vermaelen and Rafinha Alcântara (also out with a knee problem) in the injured list.
More updates as they become available.