Arsene Wenger will be forced to make a last-minute FA Cup final fitness decision on Shkodran Mustafi.
Defender Mustafi is confident he will be okay to play for Arsenal against Chelsea at Wembley on Saturday, but strict FA and Premier League guidelines on concussion may mean the decision is taken out of his hands.
The Germany international has missed training this week as he needs the all-clear after taking a blow to the head in the win over Sunderland last Tuesday night, and there is a growing fear he is running out of time.
Per Mertesacker, who made his first appearance all season after injury as a sub in last Sunday’s Premier League finale against Everton, is the back-up option to play in a back three alongside Nacho Monreal and Rob Holding.
Boss Wenger did consider reverting to a four-man defence in that game because of injuries — and as a dress rehearsal for the Cup final. He is aware that Chelsea have an outstanding record against other clubs that try to match up against them by going with three at the back.
Petr Cech is expected to continue in goal, having played the semi-final against Manchester City and with No2 David Ospina set to join Fenerbahce for £5m this summer.
Left-back Kieran Gibbs will be fit to start after a thigh injury.
Meanwhile, Arsenal have made a fresh move to hang onto Alexis Sanchez , who is a summer target for Manchester City and Bayern Munich.
Talks with striker Sanchez are continuing, and they have made an improved offer of a new deal that would pay him around £270,000-a-week.
Wenger insists they will not sell the 28-year-old this summer, even though he only has a year left on his current deal.
City are confident they will be able to tempt Sanchez into a reunion with his old Barcelona boss Pep Guardiola, while the Chile international’s representatives have already spoken to Bayern.