Foley, who has missed Richmond's past four games with a heel complaint, suffered a partial rupture of his Achilles tendon at training on Tuesday.
It continues a history of Achilles injuries for the 26-year-old.
He missed the Tigers' final nine games in 2009 and was then restricted to just four matches in 2010 by similar injuries.
Foley rebounded to play all 22 games for Richmond last year and was a key part of a strong, emerging midfield in the first part of this season.
The latest blow comes after the Tigers lost a string of players last week.
Ty Vickery was ruled out for the season with a shoulder injury, while defender Dylan Grimes faces a long absence with a hamstring complaint and Jake King is sidelined by a knee injury.
Richmond will also be without Daniel Jackson (suspension) and Dustin Martin (club suspension) for Saturday's clash with Gold Coast in Cairns, while the Tigers last week cut ties with Daniel Connors.
They copped a further injury blow against Melbourne on Saturday, when injury-prone key backman Ben Griffiths was subbed off with calf tightness.
"It's disappointing because he's actually been going really well over the last couple of weeks," Tigers elite performance manager Matthew Hornsby said of Foley on the club's website.
"He's been feeling strong and running well, with minimal pain.
"He'll have surgery to repair the tendon, which means he won't play for the remainder of 2012, but we know there'll be no problems to be ready to go for the start of 2013."