The former IRB World Player of the Year is struggling with an ongoing calf injury and may not recover in time for the opening encounter of the three-match series in Durban.

Head coach Peter de Villiers and the Springbok management have made no comment on Burger's possible absence and there has, as of yet, been no talk of a replacement.

The 26-year-old has not played a competitive fixture since picking up the injury three weeks prior to the end of his side's Super 14 campaign and has not been able to take part in full training sessions since joining up with the Boks late last month.

The loss of Burger would be a serious blow for the world champions for whom the Stormers blindside is one of the side's most iconic figures.

Burger has won a total of 49 caps for the Boks and had been destined to hit the half century mark against Ian McGeechan's tourists on June 20.

Now it appears as though Burger may have to wait until a week a later to reach that milestone, with Danie Rossouw of the Bulls the favourite to take his place at the ABSA Stadium.

Another player who could step up if Burger is forced out of action is Heinrich Brussouw of the Cheetahs. The openside featured for the Boks against a Namibian Invitational XV on May 29 but did not make the cut for the squad for the series against the Lions.

Since then, Brussouw has shown his worth with an outstanding display against the Lions for his Super 14 outfit last Saturday, leading many observers to suggest he could yet force his way into the reckoning.