The German defender insists his side can still finish strongly in 2012, and believes he is gradually adapting to life in the Premier League following his summer switch
A win on Tuesday would have seen the Gunners leapfrog Chelsea in the Premier League, but the north London side failed to do so, with visiting shot stopper Wayne Hennessey in brilliant form.
Harry Redknapp’s Tottenham then beat Norwich 2-0 at Carrow Road on Wednesday, which extended the gap between third and fourth to four points, but the German defender still believes Arsenal have plenty to play for in the second half of the season.
"We had a big chance to go into fourth place, but we didn't do that. It was our fault, we had a lot of chances but we didn't score," Mertesacker told the Telegraph.
"There are some days in the life of goalkeepers where something happens like that. He was in great form and it was his day.
"Yes, we had a big chance today, but there are other big chances to come. We are ready to go into the top four and are confident."
The 27-year-old appears to have settled into the English game after arriving from Werder Bremen in the summer, and is enjoying life in the Premier League.
He added: “It is a little different between here and the Bundesliga but you get used to everything in the world and hopefully in the next month I will improve more and more.
"I am very happy to be here and to get this opportunity to build myself up.
"It is more physical than, maybe not as technical as the Bundesliga, but the speed is much harder.
"This the best league in the world, therefore you have to improve your game, but the important thing is to show you can deal with it."