Full-back Kieran Trippier says a drop in "standards" is contributing to Newcastle's poor Premier League form, which continued with a home defeat by Nottingham Forest.
The Magpies slipped to their fourth defeat in five top-flight matches on Tuesday, and sit seventh in the table.
Eddie Howe's team have also been knocked out of the Champions League and Carabao Cup during December.
"We know we can do better," Trippier said on Amazon Prime.
"The standards we have set throughout the last 18 months, we have come away from them a little bit in the last few games.