Arsenal's stuttering title challenge in the Premier League could fizzle out completely if the team fails to beat struggling Blackpool at Bloomfield Road on Sunday.
"The way we respond now until the end of the season is hugely important for us because we have worked so hard since the start. It's very important we battle until the end," Wenger said.
Blackpool lost 6-0 at Arsenal in August and has won just twice in 2011 but will be fighting for its topflight survival after slipping to 17th position in the table, just a place and a point above the relegation zone.
Arsenal cannot afford another setback to its title push, with dissenting voices regarding Wenger and his young side beginning to be heard inside and outside the Emirates. The Arsenal Supporters Trust spoke of its "considerable disappointment" on Thursday at the Gunners' recent results.
"Now it's a crucial moment where we have to trust these players and not listen to some opinions of people who have not worked half a day in football," Wenger said.
United, which is seven points clear of Arsenal having played a game more, takes on Fulham at Old Trafford without suspended striker Wayne Rooney.
The England international will serve the first match of a two-game ban for swearing directly into a television camera, despite an appeal from United.
"It will bring us together - it's a plus for us," said United manager Alex Ferguson of Rooney's absence.
Ferguson will be without his in-form striker but United's recent defensive problems have eased, with center back Rio Ferdinand recovered from a calf injury and both utility defenders John O'Shea and Wes Brown fit again after hamstring problems.
The only defender out for United is right back Rafael da Silva, who hurt his knee in the 1-0 win over Chelsea in the first leg of their Champions League quarterfinal match on Wednesday.
With the second leg on Tuesday, Ferguson must decide whether he needs to rest some of his key players.
Fourth-place Chelsea returns to domestic duty with a home match against bottom club Wigan, and is currently embroiled in a fight with Manchester City and Tottenham for a finish among the Champions League qualification places.
The reigning champions are a point behind City, with a game in hand, and five ahead of Spurs. They should be confident of success against Wigan having scored 14 goals in their last two matches against Roberto Martinez's strugglers.
"Wigan will be a very important game because they are fighting to survive and we have to be ready for them," Chelsea manager Carlo Ancelotti said.
"Wigan are playing very well, didn't concede against Tottenham last weekend. It will be a different game tomorrow to our last games."
"It's a strange moment for him but I have confidence in him," said Ancelotti, the former AC Milan coach. "And he still has confidence in himself.
"(Hernan) Crespo didn't score in his first six months at Milan. This is the life of a striker."
Ancelotti said Brazil center back Alex will be on the bench at Stamford Bridge after recovering from a knee injury.
City visits sixth-place Liverpool on Monday and Spurs host Stoke on Saturday.
At the other end of the table, seven points separate the bottom 11 teams.
Second-bottom Wolverhampton, which a point above Wigan, is at home to Everton, West Bromwich Albion visits Sunderland and third-bottom West Ham is at Bolton.
Aston Villa, which is 16th and only two points above the bottom three, hosts Newcastle on Sunday, while Birmingham travels to Blackburn in the weekend's other match.
