The world champions are on their worst run of results for two decades having lost their last five Tests.
They have only a 42% success rate in the three years since beating Australia to win the Webb Ellis trophy in Sydney.
To make matters worse, injuries mean England head coach Andy Robinson has this week been without 23 of his 40-man elite squad for the first training camp of the season at Loughborough University.
The state of the squad could not be in starker contrast to this time four years ago when Sir Clive Woodward was masterminding the 2003 World Cup campaign.
They beat Australia and New Zealand at Twickenham in November 2002, won the 2003 Six Nations Grand Slam and then completed historic victories over the All Blacks and Wallabies on enemy soil.
But England cannot buy a victory at present and Leonard admits the odds on a successful World Cup defence in France are growing "longer and longer".
But the world's most-capped prop, and veteran of four World Cups, two finals and one winners' medal, insists all is not lost.
"The perfect build-up to a World Cup is what England had in 2003 when we won 18 out of 19 Tests," he said.
"The only game we lost was by a point to France in Marseille.
"But that is not always necessary. I have seen Australia win the World Cup in 1991 and South Africa in 1995.
"Before the 1991 World Cup, Australia were getting thumped by everybody. Two years prior to South Africa winning the 1995 World Cup, they were getting beaten by everybody as they came out of isolation.
"Those performances prior to 2003, when England had that great run, has now made a rod for our own backs. And three years on from the World Cup we are still in a transitional period.
"Yes, they are up against it because their performances since the World Cup have not been good enough.
"The players have underperformed - but I know they are great players.