Shearer, one of England's most prolific strikers of recent times, believes that without Rooney's goalscoring prowess, it will be impossible for Fabio Capello's team to bring home the trophy for the first time in more than half a century.
"Wayne Rooney to England is the same as Wayne Rooney to Manchester United," Shearer said on Monday.
"He's a huge player. If he were to get injured between now and the World Cup, it would be a disaster. Could it kill their hopes? Absolutely."
Rooney has scored 26 goals in all competitions this season, including four in one game against Hull City last month.
"We've always known about Wayne's passion and skill but now he is scoring goals on a regular basis," said Shearer.
"He's getting the reward for channelling his energy in the right way. The best thing that has happened to Wayne was Cristiano Ronaldo leaving United. He's filled the gap brilliantly."
An iconic figure in English football who scored 30 goals in 63 appearances for his country in the 1990s, Shearer shrugged off suggestions that John Terry being stripped of the England captaincy earlier this month following damaging media revelations about his private life would harm England's chances.
Speaking at the unveiling of supermarket chain Morrisons as the latest sponsor for England's 2018 World Cup bid, Shearer, the former Newcastle United manager who has resumed his career as a TV analyst, said: "I don't think morale in the camp will be a problem."
"If England don't win the tournament, I'm sure the accusations will fly around but it will be down to lack of ability or bad luck. I don't think what has happened will harm England's chances or affect John Terry's game.
"John Terry is still a great leader but England have others in Rio, Steven Gerrard and Rooney.
"Besides, there's enough time between now and the World Cup. I can't comment on whether Fabio Capello was right to sack John Terry. What I can say is that the manager will be a big player for England in terms of the group mentality."
