England opener Jason Roy is optimistic he will return from a three-game absence to face India in the Cricket World Cup on Sunday, captain Eoin Morgan has revealed.

A hamstring injury meant Roy was sidelined once again on Tuesday when the tournament hosts fell to a 64-run loss to Australia, denting their semi-final aspirations.

Morgan's side have lost two of the three matches Roy has missed, with his deputy James Vince dismissed for a second-ball duck against Australia after scoring a combined 40 in his previous two knocks.

Roy took part in practice on Monday and Morgan said the 28-year-old believes he will be ready to take on India at Edgbaston in a match which has suddenly become crucial for their last-four hopes.

"I think with four days of rehabilitation, he's hopeful of being fit," Morgan told Sky Sports.

"But if it's a big risk, we'll play it as it is."

Roy smashed 153 in his last innings against Bangladesh on June 8 but pulled up in the field when chasing a ball in England's clash with West Indies.

Without him, England were bowled out for 212 against Sri Lanka in a 20-run loss at Headingley last Friday, while they were dismissed for 221 when chasing Australia's 285-7 on Tuesday.

Their explosive batting was considered a large reason why they were made pre-tournament favourites and Morgan insisted it was too simplistic to think Roy's absence was the only reason for their struggles.

"I think our basics get challenged a lot more when we don't play on batter-friendly wickets, when you probably have to rotate the strike a lot more, as opposed to find the boundary more often," he said.