Bulgaria's preparations for Saturday's World Cup qualifier against Ireland in Sofia have been hit by a defenders injury crisis.

Litex Lovech star defender, Mihail Venkov, who was only recently called up by Bulgaria coach Stanamir Stoilov, has pulled out of the squad after sustaining a knee injury in training on Thursday. He joins fellow defenders Zahari Sirakov and Alexandar Tunchev on the sidelines.

The Energie Cottbus midfielder Stanislav Angelov is also doubtful with a groin injury.

On the positive side, Bulgaria will welcome back star trio Dimitar Berbatov, Valeri Bojinov and Martin Petrov into their starting line-up after they had missed recent games for their country because of injury.

"We know that Ireland will be searching for a positive result and I expect a very tough encounter," Stoilov stated Thursday.

Bulgaria are third in Group Eight with seven points from five matches. Italy top the standings with 14 points from six matches followed by Ireland on 12.