Lacazette joined Arsenal from Lyon last summer, and the Frenchman has scored nine times in 28 appearances for his Premier League club during the 2017-18 campaign.
The 26-year-old has only netted once in his last 12 Premier League appearances, however, and has seemingly lost his starting role at centre-forward to January arrival Pierre-Emerick Aubameyang.
Petit has claimed that Lacazette's Arsenal career could be coming to an end just seven months after making the move.
"Lacazette is under massive pressure. He needs to improve or face the exit this summer. Aubameyang's signing tells me it might already be too late," The Sun quotes Petit as saying.
"Arsene Wenger's belief in Lacazette has gone. After six months his statistics are not exactly tremendous. Auba is exactly the man Arsenal need."
Aubameyang is expected to lead the Arsenal line in Saturday's North London derby with Tottenham Hotspur.