The Official Online RBS 6 Nations Store is open. The store has everything you need to get behind your team during the RBS 6 Nations, plus the store is now fully stocked with a much wider range of rugby merchandise.
Croft, 27, played in Sunday's Aviva Premiership opener against Worcester, but damaged his anterior cruciate ligament and had surgery on Tuesday.
After an injury hit spell on the sidelines; Croft returned to form at the backend of last season and won selection ahead of international skipper Chris Robshaw for the Lions tour of Australia.
"We felt it was relatively innocuous but the ACL was ruptured," said Tigers director of rugby Richard Cockerill.
Croft, who also featured in three Tests for the Lions against South Africa in 2009, has been capped 38 times by England since making his debut against France in 2008.
Cockerill added: “Its horrendous bad luck for Tom because it is only last year that he came back from a very bad neck injury and did so well for England and the Lions as well.
"But these things happen. Tom will make a full recovery but it's his season over. It's a blow but we have just got to get on with things."