Ruud van Nistelrooy will miss the remainder of the Spanish season after suffering a knee injury. The Real Madrid striker travelled to the United States to see Dr Richard Steadman, and after undergoing an exploratory operation it has been decided the Dutchman will now need further surgery.

"The estimated time he will be out is from six to nine months, depending on the recovery," a Real Madrid statement said. "Following an exploratory arthroscopic operation on Wednesday, it was determined that Ruud van Nistelrooy had a partially torn meniscus in his right knee.

"Real Madrid's medical staff, Dr Steadman and the player decided to surgically repair the damaged knee."

Steadman operated on Van Nistelrooy in 2000 when he suffered ligament damage to the same knee while at PSV Eindhoven.

Van Nistelrooy's most recent appearance for Madrid came in last week's 2-0 home defeat by Juventus in the Champions League, when he was substituted nine minutes from time. Losing the former Holland international is a further blow for Madrid and their coach Bernd Schuster, who has found himself under increasing pressure following a run of poor recent results.

There have even been suggestions in the Spanish press that Schuster could lose his job this weekend if Madrid do not win their Primera Liga match at Real Valladolid.

Van Nistelrooy joined Madrid in 2006 from Manchester United and in his first season at the Bernabeu, scoring 25 league goals to finish as the Primera Liga's leading scorer. Madrid won the title that year, and they successfully defended it last season when Van Nistelrooy, despite sitting out part of the campaign with an ankle problem, netted 16 more goals.

This season Van Nistelrooy has scored seven goals in ten competitive appearances.