Merson claimed that Arsenal "are the worst team in the country without the ball" as he blasted his former side on the radio.
"One team was playing in a cup final, the other team looked like they were playing a testimonial. I don't like saying players weren't putting the effort in, but some of them looked beaten when the first goal went in, and that was it," Merson told talkSPORT.
"It was like they all thought, 'we're not winning here' I knew they couldn't do what Wigan did against City. Wigan without the ball are a better football team than Arsenal. They are the worst team in the country without the ball, and it was proven again yesterday.
"When they haven't got the ball too many of them don't see danger, they don't close down. They never close down as a group, it's all individuals.
"You see Man City press and they all go at the same time, they all know what they're doing, but with Arsenal, nobody knew what they were doing. When the first goal went in, I just turned to my wife and said, 'this could be any score you want'."
Arsenal will again face City on Thursday night at the Emirates Stadium in the Premier League.