Arsenal boss Arsene Wenger admitted his side would struggle to claim a top-four Premier League place after
their 2-1 defeat at rivals Tottenham.
Arsenal are seven points behind third-placed Spurs and five behind Chelsea in fourth with 10 league games left.
"We have to fight and it will be difficult now, because we dropped points that we couldn't afford to drop," said the Frenchman.
Can Arsenal produce a repeat comeback?
Arsenal beat Tottenham in the derby on 26 February last season to move seven points behind their rivals - a gap they eventually overhauled.
"But we will fight and we will keep our spirit."
Arsenal have not finished below Spurs in the league since 1995 and outside the top four since 1996, when they finished fifth.
They are currently in their 15th consecutive season of participation in the Champions League.
However, they are 3-1 down after the first leg of their Champions League tie against Bayern Munich in London with the return on 12 March in Germany.
And their hopes of hopes of qualifying for European football's elite competition via a top-four finish suffered at White Hart Lane, where the Gunners were punished for a spell of poor defending late in the first half.
Gareth Bale and Aaron Lennon capitalised to score twice for Spurs in the space of three first-half minutes.
"At times against Arsenal, Tottenham played like they were the away side. With the Gunners also keeping that high defensive line, they made things even easier for Bale."
Per Mertesacker's header went in off Bale to give Arsenal hope after the break but Tottenham held on for a vital three points.
"That was very important," said Spurs boss Andre Villas-Boas. "It meant a lot for our fans - we wanted to get this one over Arsenal and create a distance between us.
"Seven points is not big enough in the Premier League, because this time last year Arsenal came back [from a similar deficit].
"We aim to continue doing well, but we have difficult fixtures coming up against Manchester City and Liverpool. We will try to push on and qualify for the Champions League."
Wenger's side defeated Spurs 5-2 last season at Emirates Stadium with 12 games to go
to reduce the deficit between the two teams to seven points - and Arsenal went on to overhaul their opponents and claim third place.
Tottenham claimed fourth but their place in the Champions League was taken by Chelsea, who finished sixth but
won Europe's top competition.
Victory was for the fans - Villas-Boas
Wenger knows his side will have to improve defensively if they are to stand a chance of repeating a similar comeback this season.
"In the first half there was nothing [in it] and then we were 2-0 down. I don't know how it happened," added Wenger.
"We produced a great energy level from the first to the last minute, but we were not decisive enough in our box or their box.
"At the back, we played offside in a position where we shouldn't have done it.
"I feel sorry for the team and the fans, because when you produce so much in a game and come away with so little it's a big disappointment.
"I feel we were on top of the game when we conceded the goals, and that is most frustrating. If you're dominated and the opponent scores you can accept it, but the way it happened is difficult to swallow."