Per Mertesacker looks set to be ruled out of Arsenal’s derby against Chelsea although the  defender has escaped any serious ankle ligament damage. Mertesacker, captain during the long absence of Mikel Arteta, limped off during the second half of the FA Cup semi-final against Reading at Wembley on Saturday. There were fears of a serious injury for the 6ft 6in German after he twisted the joint but subsequent scans have shown it is a minor sprain. Per Mertesacker will miss Arsenal's visit by Chelsea on Sunday due to an ankle injury . The stand-in Gunners captain went down in Arsenal's FA Cup semi-final win over Reading on Saturday . He is not expected to be fit in time for Sunday, however, and likely to be replaced at centre-half by Gabriel Paulista, who has started three times in the Barclays Premier League since he was signed in January from Villarreal. Chelsea come into the match with a 10-point lead over their London rivals and will need to capitulate in spectacular fashion to not take the Premier League title. Second-placed Arsenal, on 66 points, lead Manchester United on 65 and Manchester City on 64. Scans showed the 6ft 6in German had just a minor ankle sprain when a more serious injury was feared . Mertesacker was substituted around the hour mark by Gabriel Paulista, who will deputise for him on Sunday .
Per Mertesacker twisted his ankle in FA Cup semi-final at Wembley .
Scans revealed the stand-in Arsenal captain escaped serious injury .
Arsenal beat Reading 2-1 after extra-time in Saturday's match .
They host Premier League leaders Chelsea on Sunday at 4pm .
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