London - Nathan Hughes and Courtney Lawes will undergo knee surgery this week after picking up injuries in England's Six Nations defeat against France, the Rugby Football Union said on Wednesday
"Hughes is expected to be out for 12 weeks while Lawes will require 14 weeks of rehabilitation," the RFU statement said.
England's final match of the tournament is at Twickenham on Saturday against Ireland, who have already been crowned Six Nations champions.
Hughes, who also missed the opening two rounds of the tournament, limped off midway through the first half at the Stade de France on Saturday after taking a heavy blow to his left knee but Lawes was able to complete the match.
Dylan Hartley is set to lead England against Ireland after recovering from a calf injury.
Hartley missed the 22-16 defeat by France in Paris that ceded the title to Joe Schmidt's men, but defence coach Paul Gustard has revealed that the Northampton hooker has played a full role in training this week.
British and Irish Lions wing Elliot Daly has been passed fit for the match after overcoming a foot injury suffered in Paris.
Head coach Eddie Jones will name his side to play Ireland, who are chasing the Grand Slam, on Thursday.