Gennaro Gattuso is expected to be out of action for six months as he will undergo surgery on knee ligaments he damaged during AC Milan's 1-0 Serie A victory against Catania on Sunday.
The 30-year-old midfielder picked up the knock in a tackle early on at San Siro and though he completed the match, a scan revealed damage to his anterior cruciate ligament.
The Italian international was subjected to tests by a specialist in Antwerp and now requires surgery.
"I have had many challenges during my career and I'll take this problem as a new one," said Gattuso. "I will try to return earlier than expected."
The setback is a huge blow for Milan coach Carlo Ancelotti, who already has injury concerns in midfield.
The Catania win that maintained the Rossoneri's hold on joint-second place in Serie A came despite the absence of Massimo Ambrosini, Andrea Pirlo and Clarence Seedorf. Ancelotti will hope to have the trio back in time for Sunday's showdown at rivals Juventus.
Gattuso will also be missed for the national side, and is likely to sit out Italy's 2010 FIFA World Cup qualifiers against Montenegro and the Republic of Ireland in March and April.