With the club struggling to bring in the big-name players fans were expecting, injuries to the existing squad ahead of Saturday's home match spells even more frustration.
Santi Cazorla's fitness will be assessed after his return from Spain's international friendly in Ecuador, while fellow midfielder Mikel Arteta has a slight thigh problem.
Theo Walcott limped out of England's 3-2 win over Scotland on Wednesday with a knee injury, although initial reports suggested no serious concerns, Wenger said.
Full back Nacho Monreal is definitely out and will not return to full training for another 10 days following a back injury, Wenger told the club website (www.arsenal.com).
Defender Thomas Vermaelen (back) and midfielder Abou Diaby (knee) remain long-term absentees.
Wenger, despite failing to win a trophy for eight years, has managed to deflect major criticism by securing Champions League places and said he was confident the club would add to its squad before the end of the transfer window.
Despite the club having money to spend, 20-year-old French youth international Yaya Sanogo is the only player to move to the Emirates Stadium.
Arsenal have been chasing Liverpool's Luis Suarez without success and fellow striker Gonzalo Higuain, who moved to Napoli from Real Madrid instead.
On Thursday, German media reports said the north London club could also miss out on signing Bayern Munich midfielder Luis Gustavo with the Brazilian reportedly heading for Wolfsburg.
"We are in a situation like Manchester United, like Chelsea, where everybody expects signings and at the moment not a lot has happened," Wenger said.
"There are 18 days to go, so that is a long time in the transfer market and we will be active.
"I cannot certify what the number (will be) but we will be active until the end, that is for sure."