Ghana coach Ratomir Dujkovic believes his World Cup side have been seriously hampered by the absence of Michael Essien at the African Nations Cup finals and will be hard pressed to live up to their new-found reputation.

However, their opening round opponents Nigeria could take the field without their inspirational midfielder Jay-Jay Okocha for the Group D match in Port Said on Monday.

A thigh injury kept Okocha out of training on Saturday and he is doubt for the game between two long-standing rivals.

Dujkovic said the absence of Chelsea midfielder Essien and two other key players, Sulley Muntari and Asamoah Gyan, through injury would severely weaken his side for the tournament.

"We cannot expect too much without these players, them not being here is a big problem for us," he told Reuters.

Dujkovic said Ghana were hopeful of success at the event but would not be as competitive as desired.

Essien was injured this month while playing for the English champions against West Ham.

Gyan had an operation last week after an injury sustained while Ghana were preparing for the tournament in Tunisia two weeks ago.

Captain Stephen Appiah is due to return to squad training on Sunday after flying to Turkey to play for his club Fenerbahce in Friday's 3-0 win over Genclerbirligi.

The disruption, added Dujkovic, had made his side underdogs for the meeting with Nigeria.

The Super Eagles, one of the pre-tournament favourites, arrived in Egypt on Friday, the last of the 15 visiting teams at the tournament.

Okocha picked up his injury in the pre-event training camp in Portugal but told reporters he was hopeful of being fit in time.

The Bolton Wanderers midfielder was named best player at the last Nations Cup in Tunisia.