Arsenal and England striker Danny Welbeck is expected to be out till Christmas after having a knee operation.
Injury to former Manchester United forced Arsenal to enquire for availability of Edinson Cavani and Karim Benzema but the club failed to sign either of them.
With no new arrivals, Oliver Giroud is the only recognized striker in the Arsenal squad.
Theo Walcott, Alexis Sanchez and Joel Campbell – who has not played for the Gunners since January – have experience of operating in that position, but are mainly used by Arsenal as wide players.
“The injury to his cartilage did not respond as well as hoped and the decision was taken last week for him to undergo surgery,” said a statement.
They were the only club from the top five European leagues not to sign an outfield player during the summer.
That led to the Arsenal Supporters’ Trust calling for an inquiry into the club’s transfer policy.
“No-one wants Arsenal to buy players just for the sake of it, but we do want to see the money being invested to make the club stronger,” it said in a statement.
Manager Arsene Wenger said: “Am I happy with the investment I make? Yes, every time. You have to find the players to invest in.”