The centre-half is expected to be ruled out for up to three weeks with a calf strain sustained in Saturday's 1-0 win over QPR.
The Belgian was already playing out of position at left-back to cover for the absence of Kieron Gibbs and Andre Santos, while the Gunners are also missing right-backs Bacary Sagna and Carl Jenkinson.
"We have lost Vermaelen for two or three weeks so I have to look if I can find somebody on loan," said Wenger.
"It would be stupid for us to drop points because we don't have a left-back.
"We now have three left-backs out. Francis Coquelin came on in this position and did quite well but he is a central midfielder."