He told the club's official website: "We know they're a top class side, so it will be difficult. But we're playing some great football at the moment so we're going down there to win.
"We've come into form at exactly the right time. We started the season off a little bit sluggishly, even though we created plenty of chances. But the goals have started to come now and we're winning matches.
"It's a nice time to get Arsenal. It's our biggest challenge this season and it will be interesting to see how far we've come."
On their first ever trip to the Emirates last season United went ahead before two late Arsenal goals gave the home side victory.
And Fletcher says Sir Alex Ferguson's men are eager to erase that painful memory.
He said: "It's a match that everyone is looking forward to, especially after the disappointment of last season at the Emirates Stadium.
"To take the lead and control the game, then lose two goals late on was a big disappointment. That's something we'll look to rectify."