Barcelona forward Lionel Messi has been ruled out for between six and eight weeks because of a hamstring injury.
The 26-year-old limped off in Sunday's win over Real Betis and has a muscle tear in his left hamstring.
The Argentina international has been hampered by injuries this season and had to be substituted against Atletico Madrid in August with a left thigh problem.
He also injured his thigh against Almeria in September.
Messi picked up the latest injury after 18 minutes against Betis, with tests on Monday revealing the extent of the problem.
A Barcelona statement read: "The club's medical services confirmed that Leo Messi has a torn hamstring muscle in his left thigh and is expected to miss the next six to eight weeks.
"The first phase of Messi's recovery will be covered in Barcelona and he will then travel to Buenos Aires."
The injury will mean the World Player of the Year will miss Argentina's friendlies against Ecuador and Bosnia-Hercegovina in November as well as a number of domestic matches.
Messi, who scored twice for Barcelona in their Champions League win over AC Milan last week to secure his side's progress to the knockout stage, is set to miss their remaining two group games against Ajax and Celtic.
"He needs to take as much time as he needs, to recover and get back to his level. We need him at his best," Barcelona midfielder Cesc Fabregas told Spanish television.
"I had something similar at Arsenal. You think you're OK, but you're not.
"I had this injury and I wasn't right for up to a year and a half - it's a really frustrating injury.
"You need to take whatever time you need because if you don't it won't heal properly."