Madrid - Real Sociedad boss David Moyes has received a huge blow with the news that top scorer Carlos Vela faces a lengthy spell on the sidelines with a torn internal meniscus.
The Mexican had to be substituted early in Sociedad's 4-1 defeat to Real Madrid on Saturday and is expected to miss at least the next six weeks.
"During the game in Madrid he suffered a twisted right knee," the club said in a statement on their website.
"Once clinical examinations and scans had taken place, the existence of an internal meniscus tear was found.
"After consulting specialists to evaluate the best course of action, we have decided on surgery."
Vela's absence leaves Moyes desperately short on attacking options after seeing his attempts to bring in new recruits during the transfer window foiled.
The Basques have only managed nine goals in 10 league games since Moyes took charge in November, of which Vela has scored five.
Saturday's thrashing at the hands of the European champions leaves Sociedad still just four points above the relegation zone in 13th.