The match went ahead after kickoff was delayed for an hour.
Mertesacker said, “It was difficult to handle because we were already here in the dressing room and then we found out very late that we extended it to another hour.
"It's kind of annoying, you want to find out if you actually play or not. That was in doubt as well.
"But we wanted to play, we wanted desperately to play, not to play tomorrow or whenever. We wanted to play desperately. Eventually everyone made sure that we can continue. But it took us 45 minutes and I think we are quite happy with the way it ended, but it took us a long time to get going here really.
“Actually the atmosphere was quite positive, because the fans who were in the stadium were quite enthusiastic, and it was quite fun to play in front of two crowds battling each other, in a way.
"It felt good to be part of that, and especially when we were 1-0 down, to get back, for the fans to get back into the game with us scoring two, we finally found our rhythm, and the fans as well were happy."