Thomas Vermaelen had been earmarked to deputise at full-back after Arsene Wenger sanctioned the year-long loan departure of Andre Santos but the Gunners’ skipper is struggling to be fit for the first-leg clash on February 19.
Goal.com has learned that Vermaelen suffered a setback in his recovery from an ankle injury in training last Thursday.
The versatile defender has had an injection in the joint, which has caused him to miss Arsenal’s last two matches, and faces a race against time to be fit for the home leg against Bayern.
Arsenal are already without long-term absentee Kieran Gibbs and new signing Nacho Monreal, who is ineligible for the Champions league, while Santos is set to complete a move to Brazilian club Gremio this week.
The 29-year-old arrived in Porto Alegre on Sunday and will join Gremio on a 12-month loan that will cover the entire Brazilian season. Goal.com revealed last November that Arsenal wanted to off-load Santos after growing fed up with his lack of concentration and focus in both training sessions and matches.
With Monreal ineligible for the Bayern tie after representing Malaga in this season’s Champions League and Gibbs ruled out for at least another month, Wenger is expected to turn to Sagna to deputise at left-back if Vermaelen does not make it in what would be the club's fourth-choice option for their biggest match of the season.
The Frenchman filled in at centre-back in Arsenal’s 1-0 win at Sunderland last Saturday following the late withdrawal of Laurent Koscielny and has moved across to left-back before, most notably in the Champions League qualifier at Udinese last season.
Rookie Ignasi Miquel, 20, who came on for the last three minutes at the Stadium of Light, is another potential option but his inexperience is likely to make him only a last resort.
Arsenal are struggling for numbers at the back, with Koscielny nursing a calf injury and Carl Jenkinson facing a domestic suspension after being sent off at Sunderland.
Santos is the fourth Arsenal player to be loaned out over the last month, following Johan Djourou, Marouane Chamakh and Emmanuel Frimpong.