Arsenal boss Arsene Wenger will look to sign a defender on loan after losing Thomas Vermaelen to a calf strain.
The Belgian limped off after 54 minutes of the 1-0 victory over QPR, becoming Arsenal's fifth recognised defender to be sidelined through injury.
Wenger said: "We lost Vermaelen for two or three weeks, so I have to look if I can find somebody [but] only a loan.
"It would be stupid for us to drop points because we don't have a left-back."
The win sees Arsenal move above Chelsea and Liverpool into fourth but they are facing mounting injury problems.
Vermaelen, normally a centre-half, has been deputising for left-backs Andre Santos (ankle) and Kieran Gibbs (groin).
Meanwhile, right-back Bacary Sagna (broken leg) and Carl Jenkinson (back) are also unavailable.
"It [Vermaelen's injury] is serious enough for him not to play on Monday against Fulham or against Leeds [on 9 January]," stated Wenger.
"We now have three left-backs out. Francis Coquelin came on in this position and did quite well, but he is a central midfielder."
Wenger is set to bolster his attacking options with the two-month loan signing of former Arsenal captain Thierry Henry from New York Red Bulls.
And he is certain the 34-year-old can play alongside current Robin van Persie if needed.
Van Persie broke Henry's Arsenal record for Premier League goals scored in a calendar year with the winner against QPR, his 35th strike of 2011.
"I don't think he [Henry] will get international clearance for Monday but he has a little chance to be available for the Leeds game," Wenger explained.
"They can play together, it can hopefully give little breather to Robin as well. Thierry is there to help out. He can also help in the dressing room.
"He will bring us his class. In training, he has still exceptional class and he might surprise a few people."
Arsenal have recovered from a dreadful start to the season to finish the year in the final Champions League spot.
Wenger added: "We know one thing, if we win our games we have a chance to come back in a very strong position.
"All the big teams have to come here [to Emirates Stadium] and, if we play well, we can get points away from home also. Let's continue to grow as a team.
"We were 17th after five games, now we're fourth after 19. It's a fantastic achievement for the players who have come in, been under a lot of pressure and gelled well together.
"We keep going and try to become stronger."