Walcott's match ended after only nine minutes in Basle
Arsenal winger Theo Walcott will be out of action for up to six weeks after injuring his ankle playing for England.
The 21-year-old picked up the knock during the 3-1 Euro 2012 qualifying win over Switzerland in Basle on Tuesday.
He went straight to hospital for an X-ray after being clipped by Yves Oehri in the build-up to England's opener.
Arsenal boss Arsene Wenger said: "I thought it would be three or four days or four to six weeks - unfortunately it will be four to six weeks."
But Wenger admitted it "could be worse", adding: "We had some good news about the scan because at some stage we were scared it could be worse. But overall it is a question of patience and rehabilitation."
Wenger said of the Dutchman's situation: "That is bad news. At the start we were optimistic. Maybe a bit too much, thinking it would be one or two weeks. But the damage was bigger than expected and he will be four to six weeks."
The Frenchman is also without forward Nicklas Bendtner, who has a groin injury and is three weeks away from a comeback, while midfielder Samir Nasri is expected to return to training in the next few days after being absent since 15 August with a knee problem.
"Nasri has had a very good preparation and joins in [training] on Friday. If needed I will integrate him in the squad for Bolton but for sure he will be back for our first Champions League game against Braga [on Wednesday]."
Walcott had been in good form for Arsenal, scoring four goals in three games before the international break.
Johan Djourou and Denilson are available to face Bolton on Saturday after injury, while Sebastien Squillaci could be involved for the first time after his move from Sevilla. All three came through a reserve team run-out in midweek.
Meanwhile, Aaron Ramsey is on course for his November return. "Aaron is running," said Wenger. "He is in the normal process but he is a little bit more long-term."
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