Technically speaking, the Nike Dri-Fit fabric is designed to "to wick sweat away and help keep you dry and comfortable."
Practically speaking, and according to players for FC Barcelona, the Nike Dri-Fit fabric "soaks up sweat to become a heavy, skin-clinging nuisance," which is certainly inconvenient and also kind of gross:
Players have even taken to weighing their shirts on scales at half-time to see how much weight they have gained, according to Spain's El País newspaper.
A shirt that weighed 200 grams at the beginning of a match can weigh up to two-and-a-half times as much just 45 minutes later.
Dressing room sources told El País that players noticed during a pre-season tour of the US that the shirt "weighed a tonne" and "stuck to the body like a limpet".
They hoped the problem would not persist when they returned to the more forgiving weather conditions in Spain, but on Friday the club called a meeting with Nike to seek solutions.
Barca has "called a meeting" with Nike to discuss the jersey issue. The company says it is "working to find a solution to the problem with the shirts along with the club," and we presume that the updated shirt might not be as eco-friendly (each Dri-Fit jersey contains the recycled plastic of a dozen water bottles). And so far, no one has brought up the fact that Lionel Messi might just sweat more than most humans.