Quins will be minus Joe Trayfoot, Jack Clifford and Tom Casson for the rest of the season after the trio underwent surgeries to fix respective injuries.
Trayfoot (ankle), Clifford (leg), Casson (shoulder) and Ugo Monye all went under the knife but the former Lion is expected to return in 2013/14.
"On the positive side Ross Chisholm, injured since last August, will return to the match day squad this weekend against Sale Sharks, while Charlie Walker who sustained an injury in the Heineken Cup game against Clermont Auvergne in January, is expected to be fit for selection next week," read a statement issued by Harlequins.
"In other injury news Joe Gray and Sam Twomey, who have both suffered from knee injuries, are making good progress and are expected to play before the end of the season.
"Will Collier and George Lowe are both seeing consultants on neck injuries, with timeframes on their return to action expected following these reviews.
"There are a number of bangs and bruises to players including Matt Hopper, Tom Williams, Maurie Fa'asavalu and Nick Kennedy, which are being monitored on a daily/weekly basis."