"We will go to Manchester United and we are in a good position... we don't want to give that up," Mertesacker told the club's website (www.arsenal.com).
"We have a great chance to focus back on the Premier League and forget what happened in the last 20 minutes (against Barcelona).
"You need to have little successes on the road. We have a great chance on Sunday to do that again and show that we can compete for the title."
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Arsenal will fancy their chances against a struggling United side, who are fifth in the table and six points adrift of the Champions League places, having lost just once in their last five encounters against the Red Devils.
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by John O'Brien)
