England Eddie Jones has up to four players on standby in addition to his 32-man summer squad, RUCK understands.
The England squad arrived in Australia last week for their three-game series, which you can watch live on Sky Sports.
Sky sources understand four players at least have been told to keep in good shape in case Jones requires reinforcements down under.
The last time England toured Australia they beat the Wallabies 3-0 in the Test series. This time they face the Wallabies in Perth (Sat 2 July), Brisbane (Sat 9 July) and Sydney (Sat 16 July) and all matches will be live on Sky Sports.
The Australia squad for the England series, which will be captained by Michael Hooper, includes six uncapped players.
#1. Jamie Blamire (Newcastle Falcons)
- Age: 24
- Club: Newcastle Falcons
- Position: Hooker