Newcastle have been struggling against the drop all season, but they have picked up some encouraging results in recent times.
The Magpies have beaten the likes of Liverpool and West Ham United in recent months, and McClaren has praised his squad’s resilience, despite their defeat last night.
"The attitude has been a different class the last couple of months," McClaren said.
"We had bad results against Leicester and Crystal Palace where that was questioned but since then it has been excellent.
"I felt it was disappointing we returned to that level and that is unacceptable."
The pressure has been ramped up on McClaren, due to Newcastle’s defeat to Everton last night.
Newcastle spent more money than any other side Premier League side in the January transfer window, but they showed little signs of progression at Goodison Park.
The Magpies were second best throughout the contest, and Everton made them pay for their poor performance.
An early strike from Aaron Lennon put McClaren’s men on the back foot, before Ross Barkley struck two late penalties to seal a comfortable win.
Newcastle’s defeat leaves them two points away from safety, with their next fixture coming against West Bromwich Albion.