England prop Mako Vunipola needs surgery on his hamstring and has been ruled out for at least three months, according to England's Rugby Football Union.
The 28-year-old was injured in Saracens' 20-10 Champions Cup final win over Leinster on Saturday.
He will miss the remainder of his club's Premiership campaign but should recover in time for the World Cup in Japan in September.
"Vunipola's hamstring injury requires surgery and will take a minimum of three months to recover," the RFU said via a statement.
England play Wales on August 11 and 17, Ireland on August 24 and then face Italy in a final pre-World Cup warm-up game on September 6.
They kick off their World Cup Pool C campaign against Tonga on September 22.