Newcastle and England striker Michael Owen could be out for several months after fracturing his fifth metatarsal bone.
The 26-year-old was substituted at half-time during the 2-0 Premiership defeat to Tottenham at White Hart Lane.
The news will be a massive blow to Newcastle, who spent £17m on the player in August.
Newcastle boss Graeme Souness said: "It's a mighty blow. It's an absolute disaster for him and an absolute disaster for the club. It's a dark day for us.''
Owen has struggled with injuries in the past, suffering hamstring trouble at various points in his Liverpool career after first pulling up in a game at Leeds in April 1999.
He has scored seven goals in nine starts for the Magpies since joining them from Real Madrid, including a hat-trick against West Ham on 17 December.
To compound Newcastle's problems, goalkeeper Shay Given has a suspected broken thumb.
Vi bruger cookies for at kunne give dig den bedste oplevelse. Ved at bruge vores side accepterer du brugen af cookies. Du kan læse mere i vores persondatapolitik.