The Canaries were beaten 6-2 at St James' Park and although they had plenty of chances to score, it was the disappointing display at the back which prompted Neil's post-match comments.
Neil said: "Offensively, we looked dangerous, scored two really good goals, hit the post twice, had other good opportunities to score; but defensively as a team...
"To be honest, I thought the game was wide-open - it was a bit like a basketball match. I thought both teams were wide-open.
"It could have ended pretty much 8-8, but the opportunities we had, unfortunately we didn't score, we hit the post or whatever, and pretty much most of the opportunities Newcastle had ended up in the back of the net.""I thought both teams were really, really open and we could have score four, five or six ourselves.
"For them to score six based on the game itself, you could argue it was harsh, but we have got to defend better."
First-half goals from Dieumerci Mbokani and Nathan Redmond had the Canaries within touching distance of the Magpies at the break before Aleksandar Mitrovic and Gini Wijnaldum, who scored four on the day, fired the home side to a comfortable win.