Despite scoring three goals apiece away at Manchester United on Boxing Day and against the Gunners Pardew's side have come away empty-handed on both occasions.
With 17 minutes to go the clash with Arsene Wenger's men was all square at 3-3, with Demba Ba scoring twice and Sylvain Marveaux tapping in, before Arsenal moved up a gear.
And the former West Ham and Charlton boss is aware some of his side's defending was unacceptable.
"The last 15-20 minutes was a fresh team against a tired team and perhaps a bit of inexperience on our bench resulted in the scoreline," he said.
"We're just so disappointed that we didn't get something out of it before then. The goals we conceded before then were not, not good and that's been our problem.
"For 70 minutes it was pretty tight, I thought we were giving a good account of ourselves but their freshness and the brightness towards the end of the game was just too much for us and we couldn't cope.
"The game really hurt us today but we know at the back we need to do better."