Newcastle boss Steve McClaren questioned his players' application following their 6-1 hammering at Manchester City on Saturday.
The Magpies led 1-0 but were then swamped by a rampant City side, particularly in a 13-minute second-half spell in which Manuel Pellegrini's men scored five times.
Sergio Aguero grabbed four of them - and five in total - and McClaren was not impressed by his side's capitulation.
Asked if he was concerned by his players' desire during that period, the former England manager said: "It's bound to be an issue. We conceded five goals in 13 minutes so we have an issue there.
"Once we conceded the third goal we need to handle it better.
"We let ourselves down in that 13-minute spell but give credit to City.
"We have shown what we are capable of and what our weaknesses are. We have to toughen up and get ready for the next spell of games."
Newcastle were excellent in an opening spell that produced a first goal for the club from striker Aleksandar Mitrovic. And, despite the scoreline, McClaren insisted there were positives to take.
He added: "I think we carried on the level of performance from last week [a 2-2 draw with Chelsea].
"We came here to win, were bold in our 4-4-2 and in that first half we really shook Manchester City. We scored the first goal, we scored a second that was disallowed which was onside and we had other opportunities.
"The goal just before half-time was the goal that gave them a lift and in the second half we got done by Aguero. His finishing was world class."
The defeat meant Newcastle slipped back to the foot of the Premier League table but McClaren believes he will get it right in time.
"We knew it would be a tough job. We know what needs to be done and it can't be turned around in a short period of time. It needs patience," he said.
"We've seen over the last two weeks the work that has been done. In the first half we looked a very good Premier League team. In the second half we didn’t look a very good team. We need to produce for 90 minutes."
