EXCLUSIVE | By Arsenal correspondent Tony Hughes

Per Mertesacker has passed a late fitness test ahead of Arsenal’s Premier League showdown against Chelsea on Sunday afternoon, Football Insider sources understand.

Mertesacker had been rated ’50-50′ by manager Arsene Wenger after limping out of the FA Cup semi-final win over Reading last Saturday with an ankle injury.

Football Insider has learned that the defender, 30, has been passed fit and is set to be reunited at the back with regular centre-back partner Laurent Koscielny.

Speaking at his media briefing ahead of the fixture at Emirates Stadium, Wenger had said Mertesacker faced a race against time to be fit. “He’s still in the treatment room and I don’t know if he will be available or not,” explained the manager. “[He is] 50/50 [to start against Chelsea] at the moment.”

January signing Gabriel had been on stand-by to partner Kosicelny if Mertesacker missed out but Wenger is likely to opt for the World Cup winner’s experience.