Arsenal striker Nicklas Bendtner will be sidelined for four weeks.
The Denmark international came off the substitute bench to shoot the Gunners ahead but sprained his ankle in the process during the club’s New Year Day win over Cardiff at the Emirate Stadium.
The 25-year-old missed Saturday’s 2-0 home win over fellow London rivals Tottenham.
Wenger had been wary of the length of time the striker was going to spend on the sideline, but disclosed after the FA Cup third round win that “”Bendtner [is out] for one month.”
Top scorer Olivier Giroud also missed the clash due to a slight illness while Theo Walcott was stretchered off the pitch with an injury.
“Theo has a knee problem, we don’t know if it is a stretched ligament or just a kick.”
Wenger had earlier admitted he may have to delve into the transfer market to bolster his thinning options upfront, pending the length of Bendtner’s stay on the sideline.
With the nature of Walcott’s injury not yet confirmed and the status of Giroud’s ankle injury not fully recovered, the Frenchman will have to keep his fingers crossed with the transfer window now open.
Arsenal are monitoring Bayern Munich striker Mario Mandzucik, who could opt for a move away from the Allianz Arena following the forthcoming arrival of Robert Lewandowski.
But any deal for the 27-year-old Croatian is unlikely to come alive this month.
Atletico Madrid striker Diego Costa has been watched by Gunners scouts, while there is also a firm interest in taking Real Madrid youngster Alvaro Morata on loan.