Leeds Rhinos forward Brett Delaney has undergone knee surgery and will spend the next three weeks on the sidelines.
The Australian aggravated a long-standing problem during last week's victory over Castleford and was forced to withdraw from the Exiles squad to take on England this Friday.
And Leeds booked Delaney in for an operation despite their ongoing injury problems elsewhere.
Coach Brian McDermott said: "Brett has been in sensational form for us but it has got to the point that we need to get him in for a clear-out to give him the best chance of performing at his best for the remainder of the season."
McDermott is already without Carl Ablett, Stevie Ward, Joe Vickery, Danny McGuire and Kallum Watkins, while Kylie Leuluai could also be missing against Widnes on Monday night.
The prop has joined up with the Exiles despite a knee injury which is unlikely to stand up to two games in four days.
McDermott said: "He could be right for the Exiles on Friday but, if he is, I doubt he will be able to play on Monday. We will have to wait and see."