Fabregas hurt the ankle in the final minutes of Barca's 3-1 win against a Malaysia XI side and will undergo further test this week to determine the severity of the injury.
. @cesc4official has sprained his left ankle. The player will undergo further tests to determine the severity of his injury.— FC Barcelona (@FCBarcelona) August 10, 2013
That doesn't sound good.
While Barcelona are understandably trying to keep things close to their vest, statements like this are often signs that there is concern there might be more significant damage to the ankle. At the risk of causing unnecessary panic though, that's just my speculation and we don't have any more facts about the injury that the tweet you see above.
It seems safe to presume, though, that Fabregas will be unavailable when Barcelona kicks off their title defense against Levante.