LONDON -- Per Mertesacker will make his first start of the season for Arsenal in Saturday's FA Cup final against Chelsea.
Mertesacker was named in the starting lineup in a makeshift back three that also includes Nacho Monreal and Rob Holding.
Arsenal had been hoping Shkodran Mustafi would recover from concussion-like symptoms in time for the game but he did not make the squad for the Gunners.
Mertesacker has only made one appearance since returning from a long-term knee injury, coming on as a substitute in Sunday's win over Everton, and has said he has never before played in a back three.
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- Arsenal FC (@Arsenal) May 27, 2017
Despite the defensive vulnerabilities, Arsene Wenger still opted to start cup goalkeeper David Ospina in favour of Petr Cech, who is on the bench.
Alex Oxlade-Chamberlain is deployed as the left wing-back rather than his normal spot on the right, which is occupied by Hector Bellerin. Danny Welbeck is preferred to Olivier Giroud up front.
Chelsea head coach Antonio Conte makes three changes to the starting XI that beat Sunderland 5-1 on the final day of the Premier League season, with Pedro Rodriguez replacing Willian in the front three.
Nemanja Matic also starts in central midfield ahead of Cesc Fabregas, who scored against his former club when the two teams met in the Premier League at Stamford Bridge in February.
John Terry, who started against Sunderland, is on the bench for his final match as Chelsea captain.
Arsenal XI: Ospina, Holding, Mertesacker, Monreal, Bellerin, Ramsey, Xhaka, Oxlade-Chamberlain, Sanchez, Ozil, Welbeck.
Arsenal substitutes: Cech, Elneny, Coquelin, Iwobi, Lucas, Walcott, Giroud.
Chelsea XI: Courtois, Azpilicueta, David Luiz, Cahill, Moses, Kante, Matic, Alonso, Pedro, Diego Costa, Hazard.
Chelsea substitutes: Begovic, Zouma, Ake, Terry, Fabregas, Willian, Batshuayi.
ESPN FC correspondents Mattias Karen and Liam Twomey contributed to this report.