After a disappointing start to the new campaign, losing each of their first three Premier League games, the Gunners have since secured two narrow 1-0 victories against Norwich City and Burnley.
Arteta continues to divide opinion among the club's fanbase, and Mertesacker – who currently works as an academy coach at the Emirates – believes the Spaniard could be in "trouble" if he oversees another poor run of form.
"He presented himself as someone who wants to lead us into these difficult moments so I could only agree but if I had known, how he reacts to difficult moments – he needs to learn fairly quickly, let's be honest," Mertesacker told The Beautiful Game podcast.
"He needs to learn super, super quick because in football, and being manager of Arsenal football club, if you lose three games on the spin, you are in trouble.
"You cannot have one or two moments of this, that's the reality of the game and the football club."
After finishing eighth in the last two league campaigns, Arsenal decided to spend around £145m on new signings over the summer, as they aim to qualify for European football and win silverware. body check tags ::