The 23-year-old was carrying the hopes of an entire nation after star playmaker Dan Carter saw his World Cup come to a premature end prior to the final pool match against Japan.
Carter picked up a similar injury to Slade in training nine days ago to send the New Zealand public into a panic as their heroes attempt to secure a first World Cup crown since 1987.
All Black boss Graham Henry called Manawatu youngster Aaron Cruden into the 30-man squad following Carter's withdrawal and the former U21 star now looks set to wear the No10 shirt in Sunday's semi-final clash with Australia.
Henry has ignored the good form of Harlequins' Nick Evans and has also added Stephen Donald to his party, with the Bath-bound 27-year-old expected to be on the bench against the Wallabies.
"We've lost the first two blokes chosen and that's a setback. That's the reality of it," said Henry, who coached the Lions in 2001.
"We have a group of players who have been on standby. We didn't announce that group and we won't announce that.
"We've got less players here than overseas. Have we got the depth? We'll find out next week.
"Last week Aaron was skateboarding around Palmerston North, having a couple of beers and watching us play. Now he's the number one 10 in the country.
"So it's a big change and a major challenge for him, but I thought he handled the situation particularly well at the weekend when he went on."
There was another bitter blow for the All Blacks after the 33-10 success against the Pumas, with first-choice full back Mils Muliaina also ruled out of the final two games of the competition.
Muliaina, who is being replaced in the squad by Hosea Gear, won his 100th cap last weekend but was forced off at half-time with a fractured shoulder that almost certainly means the 31-year-old has played his final Test.
"I really wanted to have a finish in a couple of weeks' time, but it is not to be," said Muliaina, who played in all three internationals against the Lions six years ago and is heading to Japan next season.
"The biggest thing I'll miss is the people. I've spent almost a third of my life here and it has been outstanding.
"What other job can you go to where people get out of their seats and cheer you? Or criticise you? I am just so proud and grateful for all the opportunities."