Arsenal's medical team will on Wednesday assess the extent of Theo Walcott's ankle injury, which could sideline the England winger for the rest of the month.
Walcott had been in decent form for the Gunners, scoring four goals in three games before the international break.
However, the 21-year-old - recalled by Fabio Capello after being omitted from his ill-fated World Cup squad - was taken to hospital for precautionary X-rays after turning his ankle in the build-up to Wayne Rooney's opening goal in the 3-1 win over Switzerland in Basle.
Initial fears of a break were dispelled by Capello after the match, suggesting the player felt the injury was "not a big problem".
However, even if it is just a bad sprain with no torn ligaments, then Walcott - who has a history of niggling injury setbacks - is almost certain to miss Saturday's Barclays Premier League visit of Bolton as well as the Champions League opener against Braga.
Walcott would be unlikely to be risked in the Carling Cup clash at rivals Tottenham, and may have to sit out the trip to Partizan Belgrade - but if all goes well could be fully match fit in time to face title rivals Chelsea at Stamford Bridge on October 3.