Thierry Henry says Arsenal's Capital One Cup third round win at Tottenham was "massive" for their confidence after losing two consecutive games.
Mathieu Flamini was the unlikely hero in the 2-1 win at White Hart Lane, scoring twice to set up a fourth-round clash at home to Sheffield Wednesday.
And Henry, no stranger to a win in the north London derby, says the dressing room will be "buzzing" after the vital victory.
He told Sky Sports: "It is massive. Huge. Let's fast forward a bit. You don't want to go to Leicester having lost that game.
"They won the derby, and you saw how they played. They fought well, they had character, it wasn't just flamboyant Arsenal. And they won at the Lane.
"They're going to be buzzing, there will be happiness around the dressing room and the training ground, and that's always better for them to prepare for the next game."
Arsenal return to Premier League action on Saturday with the trip to the King Power Stadium to face unbeaten Leicester, having picked up 10 points from six games.
But after Manchester City's 2-1 defeat by West Ham on Saturday, Henry insists the unpredictability of the Premier League gives Arsene Wenger's side hope of challenging for the title.
He said: "I would have been more worried if Man City had won against West Ham, but they didn't. It gives a little hope after the loss against Chelsea.
"Things can happen in this league, as we all know. Nobody would have thought West Ham would go to Anfield, the Emirates and the Etihad and win.
"I still think they're going to be challenging. Are they going to be winning it? I don't know. I think I still see City being up there at the end of the season."