Unai Emery believes defeat to Chelsea on Saturday would end Arsenal's hopes of a return to the Premier League top four.
The Gunners welcome their London rivals to the Emirates Stadium knowing a loss to Maurizio Sarri's Blues would leave them nine points adrift of the Champions League places.
After enjoying a 22-game unbeaten run towards the back end of 2018, Arsenal struggled over the festive period and lost at West Ham last weekend.
Emery's side could kick off in sixth place if Ole Gunnar Solskjaer's resurgent Manchester United get a positive result against Brighton earlier in the day.
The fact United were 12 points behind Arsenal when Jose Mourinho was sacked in mid-December shows how much the north Londoners' form has slipped of late.
And Emery feels another defeat to Chelsea, following on from a 3-2 reverse at Stamford Bridge on the second weekend of the season, would spell the end of any hopes of a first top-four finish in three years.
Asked if a nine-point gap would be too big to overturn, the Arsenal head coach replied: "I think yes.
"We had a big challenge against West Ham. And the reason is because we spoke about playing under pressure, which we have to do if we are to be competitive, and take this opportunity. It is a big ambition of ours to do that.
"After our loss to West Ham it is a big difference to be six points behind Chelsea instead of three points behind.
#WHUARS pic.twitter.com/5kUIQSBN4B — Arsenal FC (@Arsenal) January 12, 2019
"But the next match is against Chelsea and the opportunity we have is not the same, but if we win we have the opportunity to be closer to them.
"And we can then continue our way in the 38 matches in the Premier League. Every player has this ambition. To play Saturday with all we can against them."
Mesut Ozil could return for Arsenal after Emery opted to leave him out of the squad for the 1-0 loss against the Hammers, with the German's future at the club called into doubt.
Emery believes Ozil's form has been too inconsistent this season, not helped by a number of niggling injuries.
The Spaniard also laid the same criticism at the door of midfielder Lucas Torreira, who has played just 76 minutes of football since the turn of the year.
"He is the same (as Ozil)," Emery replied when asked why Torreira has been relegated to a bit-part player in recent weeks.
"Sometimes he is with a good performance, sometimes he is with worse performances. And sometimes he can play and sometimes somebody else can play. I think this is normal."
