And he appeared on the bench for the second with an ankle boot on, leaving fans concerned.
Unai Emery confirmed afterwards that the 28-year-old had suffered an ankle injury but said it was “not serious”.
And footage has emerged which appears to confirm that statement.
In the clip, the players are training in the club’s gym.
Lacazette can be seen with defender Shkodran Mustafi, being filmed by Pierre-Emerick Aubameyang.
And he is working on two heavy ropes with his arms.
But the forward is doing it without the ankle boot, driving hard as he smashes the ropes into the ground.
Aubameyang is left in stitches as the Frenchman grits his teeth in mock pain.
“Push,” he shouts as the Lacazette puffs out his cheeks.
In a separate clip, the 28-year-old is sprinting on a bike machine with the German defender.
“If it’s possible, work,” Mustafi shouts.
He works his legs and arms while Aubameyang watches.
This footage was shared on the Gabon international’s Instagram story before being re-shared on Twitter.
It has already been viewed more than 15,000 times as the Gunners faithful expressed their relief.
“Happy to see he’s feeling better,” one supporter said.
Another commented: “Go Laca.”
While a third could not contain themselves.
“Thanks f*** for that,” they said.