By Bate Felix

JOHANNESBURG (Reuters) - Injuries to defensive duo John Mensah and Isaac Vorsah have forced Ghana's coach to make changes to his starting lineup for their second World Cup game against Australia on Saturday in Rustenburg in Group D.

Mensah, who captained Ghana in their 1-0 win against Serbia, picked up a knock in a pre-match training session on Friday and has been replaced by Jonathan Mensah, a 19-year-old hard-tackling center back.

Ghana's Serbian coach Milovan Rajevac had told reporters on Friday that both Mensah and fellow-defender Isaac Vorsah, who is also injured, were doubtful for the game.

He did not specify the nature of the injuries.

Lee Addy will come in for Vorsah.

Apart from those two changes, the Serbian trainer has named an almost unchanged squad that beat Serbia in their opening game, Ghana FA website ( said.

Richard Kingson will captain the side with John Pantsil and Hans Sarpei as full-backs.

Anthony Annan and newcomer Kevin-Prince Boateng have been entrusted with the midfield holding role while Dede Ayew and Prince Tagoe roam the flanks.

Asamoah Gyan will play up front while Kwadwo Asamoah will operate behind him.

(Editing by Jon Bramley)