The defender is hoping for a repeat performance after the international break.
The Gunners ran out as 3-0 winners in Sunday’s crunch clash, as they flew out of the blocks and scored their three goals inside the first 30 minutes.
They let up the pace after that as United tried to find a way back into the game, but Mertesacker and his colleague held firm to become the first side in nine games to stop Louis van Gaal’s side from scoring.
And the Germany international says that is down to everything coming together as a unit.
“We had a good understanding [defensively. I think a lot clicked,” he told arsenal.com.
“If one of us won a duel, the other would be there and that was the same in the second half. If he [Anthony Martial] ran past one of us, which can happen, someone else would be there straight away.”
Hope for repeat after international break
Mertesacker also believes that the performance showed how eager Arsenal were to put right the midweek defeat to Olympiakos in the Champions League.
The Gunners have had a disastrous start to their European campaign this season, losing to both Dinamo Zagreb and the Greek side, making qualification from this point an almost impossible task.
The victory over Manchester United has gone some way to righting those wrongs, though, and Mertesacker is hoping that they can maintain those standards following the international break.
“You could see how much the team wanted to respond [from Olympiacos],” he added.
“As a team you try and remind yourself of what you can achieve and you could see that we have a lot of confidence. I hope that we can display that again in two weeks.”