John Obi Mikel joined the Nigeria squad on Friday for the first time since knee surgery last month and will be fit for the World Cup, officials said.
The midfielder has been out of action since a minor operation last month and missed Chelsea's run-in to the English Premier League title as well as the London club's victory in this month's FA Cup final.
"He has completed his rehabilitation at Chelsea," a Nigerian Football Federation spokesman said.
Nigeria are training near Maldon in the English county of Essex and play a friendly against Colombia at Milton Keynes on Sunday.
Nigeria's opening World Cup Group B match is against Argentina in Johannesburg on June 12.
