VIDEO: Stormers back their Currie Cup locks
However, Stormers coach Robbie Fleck is confident his back-up locks – John Schickerling and Chris van Zyl will be up to the task in their opening match of the season.
They host the Jaguares in the season-opener at Newlands on Saturday.
It was confirmed on Thursday that Pieter-Steph du Toit joined fellow Bok Eben Etzebeth on the sidelines, after Du Toit failed a fitness test.
He has been struggling with his back for some time and underwent a second block on the facet joint – which involves injecting a small amount of local anaesthetic (numbing agent) and/or steroid medication into the small joints at each segment of the spine that provide stability and help guide motion.
"Hopefully the second one [block] will work now," Fleck said, adding that Du Toit injured his back again last week Thursday.
He was unable to train this week, but the coach remained optimistic.
"Hopefully he will be good to go on tour, on Sunday," Fleck said if the three-week trip that will see them play the Waratahs, Crusaders and Highlanders.
Etzebeth, who has struggled with a shoulder injury on the year-end tour, has seen a number of doctors and specialists regarding the problem and will be out for at least four months.
Asked about the absence of the two Bok locks, Fleck said he is comfortable with the back-up locks.
"These are the starting Currie Cup locks," the coach said, adding: "JD [John Schickerling] was outstanding last year and Chris [van Zyl] lead the side to victory in the Currie Cup competition.
"I have no doubt in terms of what they can do.
"They played plenty of Super Rugby for us last year.
"Eben [Etzebeth] and Pieter-Steph [du Toit] are big losses for the team, but we certainly do back whoever comes in and they did very well for the Currie Cup team last year."
By Jan de Koning