Nigeria suffered a blow just under a week away from the start of the World Cup as they announced that star midfielder

John Obi Mikel had been left out of

the squad because he did not want to aggravate a knee injury.

The 23-year-old Chelsea star - who follows club teammates Michael Ballack, Michael Essien and possibly Didier Drogba in missing out on the finals because of injury - has been replaced by striker Brown Ideye, who plays for French First Division side Sochaux.

"We have dropped Mikel from the World Cup squad after he told the team he did not want to put his career at risk as his

knee injury has yet to fully heal after a recent surgery," disclosed top team official Emmanuel Attah on Saturday morning.

Attah later announced that Ideye had replaced Mikel after a meeting of federation officials and coach Lars Lagerback.

Ideye was held up in Nigeria for about a week before he could join up with the rest of the squad

in England as a result of problems with an entry visa to the United Kingdom.

He could therefore only train with the team once before the final 23-man squad was announced on Monday.

Ideye, a former youth international, has yet to be capped at full international level by Nigeria.

Mikel, capped over 30 times, had been a huge doubt for the World Cup as he last played for Chelsea in April.

Before this big injury blow, a confident coach Lars Lagerback had been confident that Mikel would play a part in Sunday's warm-up game against North Korea.

However, others had been concerned that Nigeria were taking a big chance on Mikel after he did not play in the team's two build-up games against Saudi Arabia and Colombia.

He was the last player to join up with the rest of the squad at their training camp in Essex, England, last week and in South Africa, he cut short his work out with the team fortwo straight days.

Nigeria are drawn in Group B along with two-time champions Argentina, Greece and South Korea and play their first match on June 12 against Argentina.