The Premier League pacesetter entertain second place Liverpool next weekend, in between a Capital One Cup clash against Chelsea and a Champions League tie with Borussia Dortmund.
However, the Gunners enter the run with confidence after a 2-0 victory over Crystal Palace on Saturday.
"Palace was a good test for us and a good win ahead of the hard games to come in the next weeks," Mertesacker said.
"We wanted to come back quickly as possible as a strong unit. What we showed was good enough to respond, but there will be more tests to come and that will be crucial for the rest of the season.
"That we have started well showed for sure we have improved a lot over the last two years.
"We are in a better position. It feels much better now. We don't have to get anything back (on the other sides), so that gives us more safety and we feel much better.
"We want to surprise people more and more. That is what we need to do.
"We are in a strong and interesting position, so we are aware of it and will try to keep it - but that is the difficult thing, to keep it."