Paul Merson has warned Arsenal that if they fail to beat Watford then their 3-0 win over Manchester United will be meaningless.
The former Gunners midfielder told SkySports that the game will be a test of Arsenal's title credentials, needing to show consistency and an ability to string results together.
He predicts Arsenal will record an away win, but insists it will not be straightforward.
He said: "It will be hard, but I'm going 2-0 to the Gunners. If they want to be genuine title contenders they have to beat Watford in these types of games.
"There's no point being brilliant one week and poor the next."
Arsenal have one eye on a Champions League game at home to Bayern Munich next week, where they must avoid defeat and a third consecutive loss.
Alexis Sanchez is questionable to play after featuring twice on international duty for Chile since picking up a minor injury in the win over United, and Wenger must make his selection wisely.
His temptation may be to rest him, but if he does and Arsenal lose, the Frenchman need only look at the reaction after he dropped David Ospina against Olympiakos and the Gunners lost, to see what the fallout would be like if his side slip to defeat or even draw at Vicarage Road on Saturday evening.