Winger Jack Nowell remains a World Cup injury doubt with England staff unable to put a time frame on his return.

The Exeter player flew home from the training camp in Italy last week for a "routine surgical review".

However, doubts linger over Nowell's availability, with boss Eddie Jones naming his 31-man squad on Monday.

England play four warm-up games in the coming weeks, before September's tournament opener against Tonga in the Japanese city of Sapporo.

"We'll see how he goes - he is a quick healer," assistant coach Neal Hatley told BBC Sport.

"We are not going to discuss what the specialist said, but he is going to put in a lot of work to make himself available.

"We will see how he goes over the next week or two and then we will make a decision."

Nowell was in outstanding form at the end of last season, excelling for England in the Six Nations and putting in an astonishing individual display for Exeter in the Premiership final against Saracens.

But he injured his ankle towards the end of the Twickenham showpiece and had surgery at the start of June.

"He is a key player for us and has played a lot under Eddie and this coaching group," Hatley added.

"He's not just a good player but a good person and a good bloke to have in the squad. He is part of the glue that holds the squad together."

England begin their warm-up schedule against Wales at Twickenham on Sunday, after spending much of the past two months in training camps, but don't need to submit their final squad until 8 September.

"It's the longest period we have ever had with the players, so from a preparation point of view it has been really good," Hatley said.

"The next few games are about making sure that when we get on the plane on the 8 September we are in the best shape we can be."