Cardiff have yet to score in the league this season after losing on the opening day at Bournemouth and goalless draws against Newcastle and Huddersfield.
However, Merson is backing them to open their account against the Gunners so long as they provide themselves with enough opportunities from set-pieces.
“Cardiff will be loving this game; they live on scraps – a free-kick here, a corner there – and if they get enough of them they could cause an upset,” he told Sky Sports.
“If the game opens up and Arsenal can play then there’s only one winner.
“I don’t know why I’ve gone for 3-0, because I don’t see how Cardiff can’t score, and if they get enough free-kicks and corners before the end of the game Arsenal could shoot themselves in the foot.
“The first goal is massive – that’s not even the word, Cardiff haven’t scored yet.”
Arsenal’s defence has been criticised this season after it has leaked six goals in their opening three games and Merson believes it will take the players time to get used to Emery’s style of defending.
He continued: “If you didn’t know [Unai] Emery wasn’t there, you’d think Arsene Wenger was still manager.
“But Emery doesn’t have the personnel, this is the way the players have played since year dot. It’s hard to change things that quickly.
Merson believes Arsenal will have to break swiftly once Cardiff inevitably test the aerial prowess of their defence.
The Gunners have employed a high press so far under Emery as most Premier League teams, and indeed European sides, attempt to penetrate teams with sharp passing and the ball on the ground.
However, Neil Warnock’s side play the ball long to a big striker, typically Kenneth Zohore, to bring onrushing midfielders into play, effectively bypassing any press by going over the top of it.
“It’s hard work doing this press, it takes a lot of dedication and hard work during the week. And it won’t work against Cardiff, as they get the ball forward quickly.
“Arsenal have to move it quickly and attack quickly too.”
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