Kanu's hopes of playing for Nigeria in the African Nations Cup are fading, with the striker's chances rated only "50-50" by West Brom boss Bryan Robson. The 29-year-old, who has undergone surgery after fracturing his cheekbone, is due to see a specialist on Monday to assess whether he can play.
"It is 50-50, and whether Kanu plays any part depends how far Nigeria go in the competition," said Robson.
"I would say the surgeon's advice would be he can't play in any group stage."
Kanu fractured his cheekbone against Reading in the FA Cup on 7 January.
Nigeria's first match in the tournament is against Ghana on 23 January.
The former Ajax, Inter Milan and Arsenal forward has 39 caps for Nigeria and has scored six goals.
He has bagged five goals for West Brom this season, including both in the 2-0 victory over Tottenham on 28 December.