Barcelona's Argentina centre back Gabriel Milito will be out of action for around six months with a knee injury, the Spanish club said.

The former Zaragoza defender injured the anterior cruciate ligament in his right knee in the Champions League semi-final second leg defeat against Manchester United at Old Trafford last week.

"He will undergo arthroscopic surgery to resolve the problem next week, after which time it will be clearer how long he will be out of action," the club announced. "It will be around six months".

The 27-year-old tore the same ligament in 2001 and that injury was controversially cited as the reason for a failed move to Real Madrid in 2003.

Barca signed him from Real Zaragoza for a fee of up to 20.5 million euros last July, and he has been a key player in their defence this season.

It is a blow for Frank Rijkaard with three games left to play as he tries to secure second place and automatic qualification to the Champions League next year.

His side are third, four points short of Villarreal, and visit newly-crowned champions Real Madrid on Wednesday.

Reuters