London Irish backs Matt Williams and Terrence Hepetema will miss the start of next season with long-term injuries.
Williams, 22, faces up to nine months out with an anterior cruciate ligament injury, while Hepetema, 28, broke a wrist in September against Worcester.
The centre looks set to be unavailable until December at the earliest.
New Zealand winger Waisake Naholo and Australia lock Adam Coleman are also continuing to recover from knee and shoulder surgeries respectively.
Irish finished 10th on their return to the Premiership in 2020, winning six of their 22 matches.
But Declan Kidney’s side could only register one win from nine after the season resumed in August.
The Exiles begin the 2020-21 Premiership season at Worcester on 21 November before their first “home” match at Brentford Community Stadium against Leicester on 29 November.