London Irish duo Alex Lewington and Theo Brophy Clews both suffered injuries during the international window.
The pair will not be available to the club for the start of next season.Lewington suffered a knee injury when he played for the England Saxons during their 32-24 win over South Africa ‘A’.
"I’m really disappointed with the outcome of the injury, but I’m fully focussed on making a full recovery and contributing to London Irish later on in the season as we look to make an immediate return to the Aviva Premiership," said Lewington.
"I would like to say a big thank you for all the well wishes I received after the game and express my gratitude to the medical treatment I received in South Africa.
Brophy Clews injured his foot while playing in the England u20 side's 48-10 win over Italy. Brophy Clews is set to miss the first part of the season.
"I’m obviously disappointed to miss the rest of the World Cup and not be able to put my hand up for selection at London Irish at the start of the season," Brophy Clews said.
"However, I’ve got really good people around me helping me to get back to full fitness as soon as possible. I’m looking forward to working hard to be a part of the squad and help the club get back to the Premiership at the first attempt.