The Denbigshire-born playermade his international debut for Wales against Canada in 2008 and was recalled to Warren Gatland's squad for the 2010 Six Nations.
The heaviest player in the English Premiership at 20st 7lbs, his season is effectively over after only three matches. He will miss the former Amlin Challenge Cup champion's European campaign in which Saletake on Brive, Petrarca Rugby and El Salvador in Pool 2 of the tournament.
"It's not looking good for Eifion, he's done his ACL. We need to get the swelling down over the next week or so and he will then need knee reconstruction surgery," said Sale director of rugby Mike Brewer.