The Frenchman’s 22-year stint at the Gunners’ helm came to an end last summer after another underachieving season.
His final years with the club were dogged by factions of the club’s support protesting ‘Wenger Out’ in a defiant stand against the manager.
But Mertesacker feels Wenger was not solely to blame for Arsenal’s lack of success, and has pointed the finger at the playing staff.
In his autobiography, ‘Per Mertesacker: Big Friendly German’, he says: “When we lost one game, we often lost a few in a row. We could show off our class across six FA Cup games, but 38 League matches in 10 months were a different matter. We simply lacked the consistency all top teams need.
“You couldn’t win the League on eight defeats a year. Arsene Wenger was always the kind of manager whose belief in his team’s qualities was steady as a rock and who approached matters with never-ending patience.
“He didn’t lose his nerve during losing streaks, either. He stuck with his convictions and his players, no matter how strong the wind was blowing. It was his greatest strength.
“Wondering whether it was also his greatest weakness and whether he was he too lenient with us is, in my opinion, a little too simplistic.
“If the fans had got their way, there would have been five new top signings every year. ‘Spend some f***ing money!’ they would chorus from the stands after defeats.
“But Wenger trusted the players he had. I never met another manager who believed more strongly in his squad’s ability.”
The 69-year-old announced prior to the end of the 2017/18 season that he would be leaving Arsenal.
But he was not able to finish his tenure on a high, with the Gunners slumping to a sixth-placed finish and going out of the Europa League at the semi-final stage.
Mertesacker added: “First and foremost, Wenger saw us as human beings and he had a lot of faith in us, which is why he stood by us.
“Ultimately, we as players need to ask ourselves whether we did everything possible to justify his trust.
“Did we implement his instructions perfectly? Were we pulling together? Did we learn from our mistakes? No.
“Wenger has won three Premier League titles, which is proof enough of his standing as a manager. The team, on the other hand, had fallen short since 2004.”