Sir Clive Woodward fears England's indiscipline could deny them Rugby World Cup glory in Japan.
Woodward believes England have a "real chance" of emulating the side he led to World Cup success in 2003, but has concerns over their ability to keep 15 players on the pitch.
"There's many strengths, they've got this very powerful team," Woodward said of an England team who play their tournament opener against Tonga next Sunday.
"This is what I call an x-factor team. But quite a few of the starting XV have got a track record of losing it in a game when under pressure.
"There's been a lot of focus on the rules regarding neck-high tackles, and if you're playing (pool rivals) France and Argentina, top teams, and get a guy sent off then the chance of winning that game is going to be very difficult.
"We saw recently (Scott) Barrett get sent off for New Zealand v Australia and they had a record score against them.
"You need every single player to play under pressure and play within the laws of the game.
"That's the only chink I see (with England), they've got a real chance if they can play in the right way and keep 15 players on the pitch."
Woodward believes Australian Jones has done an excellent job since being appointed after England's failure to make the knockout stages at the 2015 World Cup.
He told BBC Radio 5 Live's Sportsweek programme: "Eddie came into the job thinking English rugby is tough and combustible, as he's called it.
"He's built an England team around how he saw England playing in the past. They are tough and very aggressive, the key thing to me is they've got to play quick.
"It doesn't matter how tough and physical you are, if you play slowly you are not going to win. If they can play at a real pace they have got every chance."
Woodward expects England to make the final in Yokohama on November 2 but concedes they will have to do it "the hard way".
On their main rivals, he said: "South Africa have come together well, it's the first time they've selected their best players from all around the world so they've got a very strong team.
"New Zealand are not quite the scary team they were four years ago, but I still think they're going to be the team to beat.
"Whoever wins that (pool) game between South Africa and New Zealand will play England in the semi-final if they go well.
"England will have to do it the hard way to win it, as they will play Australia or Wales in the quarter-final.
"But I think an England-South Africa final will be fantastic."
