The NSW Waratahs lock stocks are being tested early, with Wallabies forward Rob Simmons ruled out of their next two Super Rugby matches in South Africa and Argentina.
The experienced second rower was thought to have suffered a quad strain in Saturday's 34-27 home win over the Stormers, the Tahs first match.
But Waratahs forwards coach Simon Cron said a scan overnight revealed a more significant injury.
"We initially thought it was just a tight quad but the scan revealed a small tear," Cron said.
"Upon medical advice, we have decided to let Rob stay at home to get the full treatment."
Wallabies forward Ned Hanigan, who scored a match-winning try after the final siren on Saturday, is now expected to move from blindside flanker to the second row for next weekend's clash with the Sharks in Durban, with the Tahs not having specialist veteran cover in the lock area.
Simmons was sin-binned for a lineout infringement in the second half of his Super debut for the Waratahs.
He has been replaced in the squad by 2017 Australian under 20s representative Lachlan Swinton.
"Lachie has the flexibility to cover both lock and loose forward and with Ned likely to play in the second row, Lachie was our best choice replacement." Cron said.
The Waratahs headed to South Africa on Sunday with a squad of 27 including Fijian Drua tighthead prop Kalivati Tawake, who has yet to represent the Sydney-based franchise.
Simmons is not expected to be available until the Waratahs fourth Super Rugby game against the Melbourne Rebels, when halfback Nick Phippps and prop Sekope Kepu are also tipped to return.
Phipps has been sidelined by a calf injury, while Kepu will work on his fitness following a Wallabies-related suspension, which ends after the Sharks match.
He won't be flown to Argentina for the following week's clash with the Jaguares.
