AC Milan's 37-year-old striker Filippo Inzaghi is likely to miss the rest of the season after suffering cruciate ligament and meniscus damage in his left knee, leaving his career hanging in the balance.
"After a consultation the doctor has confirmed the need for surgery," a Milan statement said on Thursday.
Inzaghi suffered the injuries after coming on as a substitute in Wednesday's 3-1 win over Palermo which sent the Rossoneri top of Serie A.
The goalpoacher's contract is due to expire at the end of the season, meaning the injury could be career-threatening.
Milan decided against offering Brazil's Ronaldo a new deal when he suffered a similar injury two years ago but the club's esteem for Inzaghi suggests a contract extension may be available.
"It can't end and it will not end. Pippo is in our hearts and we in his," Milan's website (http://www.acmilan.com) said.
Former Italy World Cup winner Inzaghi has also kept himself physically fit in order to keep playing at the top level in his late 30s and the fact he is usually a substitute has also kept him fresh.
He bounced off the bench to score twice in Milan's 2-2 Champions League draw with Real Madrid last week and had been hoping for a role in Sunday's Serie A game with champions Inter Milan.
Brazil striker Alexandre Pato also looks set to miss the derby with a thigh problem leaving Massimiliano Allegri almost obliged to play Zlatan Ibrahimovic, Robinho and Ronaldinho.
With Milan top and aiming for their first scudetto since 2004, owner and beleaguered Italian prime minister Silvio Berlusconi may seek to buy a replacement for Inzaghi in the January transfer window to boost his side's hopes and his own popularity.