The Gunners were a class above United in their first meeting this season as they destroyed Louis van Gaal's side 3-0 at the Emirates Stadium.
Sunday's encounter takes place at Old Trafford, but Mertersacker insists that United's home-ground advantage will not count for much if Arsenal can recreate their October performance.
"I think we came out really strong, trusted in ourselves, nicked balls from them in their final third and then broke them down," Mertesacker told Arsenal Player.
"It was remarkable how we played and how we reacted.
READ MORE | Wenger worried by goal drought
"We were really active from the start, pressed them high and tried to get the ball as quickly as possible. It completely worked out. It will be a different game this time but I want to see the same effort from our side.
"That was our plan, to get the ball early, so the distance between where we got the ball and the goal was short. We are dangerous when we win the ball early. I think that’s something we need to emphasise.
"I would say we are more comfortable going there, or away from home in general, and performing well and to our best [than before]. We need a good performance in Manchester, there’s no doubt about it."
The match is a must-win for both sides as Arsenal look to stay in touch with Premier League leaders Leicester City, while United need the three points as they look to chase down a top-four spot.