The Gunners hopes of securing a top-four place looked in serious danger after the defeat at Goodison Park, with the hosts moving above them in the table.
However, a late resurgence helped Wenger’s side secure a Champions League spot at the expense of Saturday’s opponents.
Wenger told Arsenal.com, “In the quality of our performance, and even more than that in our mental resistance, the mental steel on the day [the defeat to Everton] was one of our low points.
“At the start I played with Arteta and Flamini in the middle of the park. We did not have Ozil, we had Ramsey on the bench, just coming back from injury. We played with Podolski, Giroud, and we were a bit bullied. At the back we had Mertesacker, Vermaelen, Monreal and Sagna. It was an off day, as well physically.
“[I was worried afterwards] because it was not in our hands anymore. It was in the hands of Everton. It was only their defeat against Crystal Palace at home that allowed us to get there.
“It was very tight last year. We finished with 79 points and I think it’s the first time since I arrived in England that you finish fourth with 79 points. You can look at the tables – that never existed before.
“Even if the Premier League was more interesting than ever last season, the top four teams took more points together than in any other year. For Everton, it’s the first time a team on 72 points didn’t get in the top four. It was very difficult.”