Wenger considering playing Alex Song as an emergency center back for Arsenal's Champions League clash with AC Milan

Kieran Gibbs is in the 18-man squad for the round of 16 first-leg match after recovering from a series of injuries that have kept him on the sidelines for four months but it is believed that Wenger is reluctant to rush the England international back into action for such a crucial fixture.

Goal.com understands that Thomas Vermaelen will continue at left back, where he has filled in for two months, and Wenger will replace the injured Per Mertesacker with either Song or Johan Djourou.

The Arsenal manager will make a late decision after weighing up his options on Wednesday but he is expected to go for Song alongside Laurent Koscielny at San Siro, despite Djourou’s greater experience in central defense.

The Cameroon international has played principally in the midfield anchorman role since establishing himself as a first-team regular, although he has occasionally moved back into defense in emergencies.

Goal.com revealed ahead of Arsenal’s Champions League group match against Olympiakos last September that Song would fill in at center back.

If Song steps out of the engine room, Thomas Rosicky is expected to join Mikel Arteta and Aaron Ramsey in central midfield, with Andrey Arshavin and Theo Walcott either side of captain and dangerman Robin van Persie.

Left back has been one of the problem positions for Arsenal this season, with Gibbs, who has not played since the 2-1 win over Sunderland on October 16, and Andre Santos both out for lengthy periods.

Although Wenger said in his prematch media briefing on Tuesday that Gibbs is “physically and mentally ready” and he would “find the most natural solution” to the reshuffle necessitated by Mertesacker’s absence, it is believed that the 22-year-old has been penciled in for a return to the starting line-up against Sunderland in the FA Cup on Saturday.