Manchester - England opener Jason Roy will miss the hosts' next two Cricket World Cup matches with a torn left hamstring, the England and Wales Cricket Board said on Monday.

Roy, who suffered the injury while fielding during England's win over the West Indies on Friday, has been ruled out of Tuesday's group fixture against Afghanistan at Old Trafford and Friday's match against Sri Lanka at Headingley.

Meanwhile, England captain Eoin Morgan, who suffered a back spasm in the field against the West Indies and did not bat in that match, will be assessed ahead of the Afghanistan clash but expects to play against the tournament minnows.

"England batsman Jason Roy, who left the field during West Indies' innings in the ICC Cricket World Cup fixture on Friday due to left hamstring tightness, underwent an MRI scan on Saturday in London," a team spokesman said.

"The MRI confirmed that Roy has suffered a hamstring tear. 

"He is set to miss England's next two matches in the ICC Cricket World Cup against Afghanistan (June 18) and Sri Lanka (June 21)."

As for Morgan's condition, the spokesperson said: "The spasm has settled down and will be monitored over the next 24 hours ahead of England's next match against Afghanistan tomorrow (Tuesday) at Old Trafford, Manchester."

Morgan, speaking at a pre-match press conference at Old Trafford on Monday, said he intended to play against Afghanistan after coming through an indoor net session at Lancashire's headquarters ground.

"It's drastically improved," he said of his back. "I've had a hit in the nets and I'm aiming to play tomorrow.

"I've had extra treatment and medication in the last two days which has helped me no end. 

"I had a small hit in the nets and hopefully I'm fit to play," the middle-order batsman added. 

"If the game was today I think I could play. It all depends on how I pull up in the morning."

Roy, who suffered a hamstring injury during England's tour of the Caribbean earlier this year, hit a fifty in their World Cup opening win over South Africa and then struck a commanding 153 in a victory over Bangladesh.

But he fell for just eight during England's surprise 14-run group loss to Pakistan at Trent Bridge.

Joe Root was promoted to open alongside Jonny Bairstow against the West Indies and the Test skipper responded with an unbeaten century.

But Morgan said Monday that Roy would be replaced at the top of the order by James Vince, the reserve batsman in England's 15-man squad.

Morgan, however, was confident Roy's World Cup was far from finished, with England bidding to win the tournament for the first time.

"I certainly believe Jason will play again in this tournament," he said.

"At the moment he's going to be assessed continuously over the course of the next week. 

"He's out of the next two games. So we'll see how he pulls up after that.

"He's obviously a huge part of what we've been doing. He's in the best form of his life. So he's very important."