Idris, 26, appeared to be on the verge of coming back from a two-week absence with a hamstring injury but will now undergo surgery for the second time in three years.
The latest setback could end the career of the former Kangaroos and NSW State of Origin representative, who comes off-contract at the end of the current NRL season.
The former Penrith star hid the news at a jersey reveal for indigenous round on Monday, telling media he was excited to play in Friday's clash against South Sydney.
"The hammy's fine - it's healed and it's happy days. I'm ready for Friday. It was always going to be a slow start for me considering I was out of the game for that long," Idris said.
"In saying that, from the first game to the last game that I played, there was massive improvement, a huge difference. But I always knew that was going to happen."
Idris' season-ending injury comes less than 24 hours after Cronulla forward Tony Williams also suffered the same fate while playing for Tonga against Fiji on Saturday.
Like Idris, Williams signed a one-year deal with the Sharks and finally made his NRL season debut two weeks ago with a 40-minute stint against the Tigers.
Now his long-term playing future is also up in the air.
"He has a torn ACL and will need surgery. He will see a specialist in the next few days to determine the best course of action," Sharks physio Andrew Gray said.