England are unable to put a time frame on Jack Nowell's return to action as doubt persists over his availability for the World Cup.

Eddie Jones names his 31-man squad for Japan 2019 on Monday and, if fit, Nowell would be a certainty to travel as part of the five-strong back three contingent.

But the 26-year-old Exeter wing is still recovering from the ankle injury incurred during the Gallagher Premiership final in early June.

Despite a routine surgical review completed last week, England are unable to set a date for his comeback.

"Jack is progressing. He went back to his club and we're hoping he'll be back and ready to be an option," assistant coach Neal Hatley said.

"The review with him will be ongoing. He's a good healer so we'll see where we get to with him."

Brad Shields is the most serious of England's injured World Cup contenders due to a foot injury that will take another three to four weeks to heal, but Mako Vunipola is ahead of schedule in his rehabilitation from a hamstring problem.

The schedule of four warm-up fixtures opens against Wales at Twickenham on Sunday and Hatley insists there will be no diffusing of the old rivalry despite the nature of the Test.

"No, absolutely not. No, never. It's a Test match at Twickenham so the rivalry doesn't take a back seat. It's preparation and we want to see where we are, but it's a Test match," Hatley said.

"Wales are a good side, a really good side. This will be a good test of what we've been working on over the last six weeks.

"Physically and tactically we'll find out where we are. We want to make sure that, in terms of preparation, we're taking steps forward."