The 6ft6 defender has been impressed with his side's start to the season and is keen to keep up their form against Champions League runners up Dortmund.
Mertesacker has been a central figure to Arsenal's renaissance, and his partnership with Laurent Koscielny has blossomed further since last season when the Gunners conceded the second fewest goals in the league.
Fellow German Mesut Ozil scored a brace as Arsenal produced some breathtaking football to beat Norwich at the Emirates.
The playmaker joined the club in the summer from Real Madrid for a club record £42.5million and has started the season well with the Gunners.
And Mertesacker is pleased with how he and Ozil have started and is looking forward to some big games - Arsenal face Dortmund (twice), Chelsea, Liverpool and Manchester United in quick succession.
"I think we're all looking forward to another couple of good contests," Mertesacker told bundesliga.com. "We've both started into the season well and the games against Dortmund are going to be defining ones for us."
And a win on Tuesday against Dortmund could well be defining - cementing Arsenal's place at the top of Group F.
The calibre of opposition at the Emirates mid-week will test the Gunners to their limit, but the defender wants Arsenal to play their own game, saying his team-mates are looking to play "the same kind of dominating performance we've been putting in all season."
Playing with Ozil for Arsenal and Germany, Mertesacker also plied his trade with a young Ozil at Werder Bremen and despite the former Real Madrid man's performances, he believes the dead-line day signing has even more to offer:
""He's progressing well at the moment and I think he'll show that more and more over the season. We can expect a lot more from him."