We were well beaten at Selhurst Park on Monday night to dent our hopes of a top four finish.
We were never really at the races in south London, and found ourselves two goals down midway through the first half.
Mikel Arteta made some attacking changes in the second half and we at last began to create chances, but Wilfried Zaha won and scored a penalty on the break to seal our fate.
It had been a scrappy opening 15 minutes or so before the hosts took the lead with a header from a free-kick. Joachim Anderson won the initial header back across goal and Jean-Philippe Mateta was all alone to nod the ball in.
In the main we have been excellent at defending set pieces situations so far this season, but we were at fault here.
Less than 10 minutes later we fell further behind. Jordan Ayew took a wonderful pass in his stride then curled home a finish beyond the diving Aaron Ramsdale for 2-0.
The hosts were well on top by now, and we didn't muster our first attempt on goal until the half hour mark, when Alexandre Lacazette tamely headed over from Bukayo Saka's cross.
Mikel Arteta made a bold change at half-time, bringing Gabriel Martinelli on for Nuno Tavares, and moving Granit Xhaka back to left back.
We needed to change our approach as well as the personnel though - and early in the second half Saka beat his man and drove into the area before being crowded out.
Emile Smith Rowe was presented with a good chance after an exchange of passes between Martinelli and Lacazette, but his shot lacked power.
Martin Odegaard had the next chance, but screwed a shot just wide from a decent position after being found by Eddie Nketiah.
Our best two chances of the game had come and gone. And we were swiftly punished.
Wilfried Zaha led a counter attack and was brought down in the area by Martin Odegaard. He stepped up and scored the spot kick himself.
Thomas Partey had lost possession on the halfway line to trigger the attack, and picked up an injury in the process. He was replaced by Sambi Lokonga.
Smith Rowe fired an effort goalwards as we continued to strive for a goal, but his fierce shot was blocked on the line by Marc Guehi.
Nketiah struck the bar with a dipping effort from 20 yards, but there would be nothing for the travelling Arsenal fans to cheer on the night.
WHAT IT MEANS
We're back at home this weekend as we take on Brighton on Saturday at the Emirates in a 3pm (UK time) kick off in the Premier League.
Copyright 2022 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source.