The 19-year-old had be substituted just seven minutes into the pre-season friendly at Emirates Stadium and is unlikely to feature again before the start of the season.
Arsene Wenger was positive about Wilshere's chances of being fit for the trip to Newcastle on the opening weekend, but the player revealed today that he will have a scan on the troublesome area.
Injury worry: Jack Wilshere was replaced by Benik Afobe against NY Red Bulls
He said on Twitter: 'Ankle scan tomorrow now!!', adding to a Tweet after the game in which he suggested the scan would take place on Monday.
He wrote: 'Came off today because i felt my ankle.going for a scan tomorrow will let you know.'
Wenger told reporters immediately after the 1-1 draw, at the conclusion of which fans booed the team off: 'It is not very serious. But it's serious enough that they say he will be out for the whole of next week. It's inflammation but he has not torn anything.
Spend some money: Wilshere urged his manager to spend some more money
'He is a quick healer usually and a tough boy, so I hope he will heal more quickly than the medical prediction.
'The England game is on August 10. If he's out next week, then he won't play against Benfica, so he certainly won't play in the England game.'
Wilshere's emergence last season was one of few positives in a desperately disappointing campaign for the Gunners, in which they once again finished empty handed.
Pre-season has hardly convinced Arsenal fans that the current campaign will be any different, with the only additions being Lille's Gervinho and young Charlton full-back Carl Jenkinson.
And Wilshere believes that if the club want to push on and end their trophy drought, they must add several more new faces, regardless of the futures of Cesc Fabregas and Samir Nasri, both of whom are expected to leave.
'We are not a spending club but we still managed to stay up there with the top teams,' he said. 'And we have to win things this year. Maybe if we had a few more faces we could really push on. If we get a few more players we can really challenge for the title.
'Around March and April we have to stay really strong. We are confident we can be up and around it then so we have to remain strong at that crucial time.'
Driving force: The loss of Wilshere would be a hammer blow to Arsenal
Meanwhile, Wenger is keen to keep Japanese star Ryo Miyaichi at the club this season and claims he will fight against the work permit issues that could prevent him staying.
The 18-year-old spent last season on loan at Feyenoord while awaiting the clearance needed to play for his parent club.
'My plan is to get a work permit for him and to put him on the pitch for Arsenal Football Club,' Wenger said.
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