Head coach Trevor Bayliss admits England are missing Jason Roy's influence but will not gamble with his fitness for the crunch game against Australia.

Roy has missed the last two games with a torn hamstring and was conspicuous by his absence in the surprise defeat to Sri Lanka at Headingley.

There is an acknowledgement in the dressing room that England were too timid in pursuit of a modest 233, with captain Eoin Morgan suggesting they neglected the basics and Jos Buttler bemoaning a "passive" display as they lost by 20 runs.

One of Roy's biggest strengths is his ability to inject adrenaline into the innings from ball one and prior to his injury he was in prime form, averaging 82 in his first seven ODI innings this summer.

The Surrey man has been targeting a return in Tuesday's Lord's date with Australia but that already looks touch and go, with the 28-year-old moving gingerly while fulfilling 12th man duties in Leeds and with just two days of net practice to come.

"If someone of Jason's ilk is not playing of course you're going to miss someone like that," said Bayliss.

"That's the game. He's injured and I'm not exactly sure when he'll be back, but we are looking forward to him coming back.

"We're not going to risk him that's for sure. We'll play each game as it comes and get the medical people to let us know whether they think he is right for the next game. If he's not, well we'll do the same heading into the next game."

Doing the same means another opportunity for James Vince at the head of the innings. The Hampshire man was not expecting to be involved in the tournament until Alex Hales' off-field indiscretions saw him axed from the provisional squad, and his record is far from stellar.

In 10 completed innings at this level he averages just 26.50, with a top score of 51, and he has weighed in with inconsequential knocks against Afghanistan and Sri Lanka since stepping into Roy's boots.

Asked if he found Vince's productivity infuriating, Bayliss responded: "Not as infuriating as it is for him.

"He looks a million dollars then he finds a way to get out. Hopefully he's one of those guys who can put one together and it tips him over the edge and he gets a string of big scores. He's certainly a good player, but he'll be looking to play a longer dig."

England versus Australia is always a hotly-contested fixture, whatever the circumstances, but the stakes are particularly high with the tournament hosts facing a fight to reach the last four.

With likely semi-finalists India and New Zealand also on the horizon, the margin for error is narrowing fast.

"Sri Lanka are one of those teams who are very unpredictable. The three teams we've got coming up are good teams and we know what we're going to get from those three teams," said Bayliss.

"We didn't play as well as we'd like in this last game and maybe we let one slip, but we have been in this situation before and it hasn't stopped us coming out and playing well in the next game.

"We'll be looking to bounce back and play a good game. We know what we can expect from those three good teams that we've got to come so I think our minds will be on the job.

"You're not safe until you've got enough points and nobody else can get past you. There's certainly two or three teams that can get past, even if we had won this one, so it just makes it a little bit tougher."

Top of the agenda will be a more proactive display with the bat, following Roy's example regardless of whether he makes the XI or not.