Newcastle boss McClaren insisted he was right to tear into his players in midweek following the 3-0 home loss to Leicester City, despite receiving another thumping at Selhurst Park.
The former England manager expects to lose the fans' backing after a seventh loss in Newcastle's last 11 league matches cemented their relegation battle.
"I said to the players 'back to work tomorrow morning'," McClaren said, after Yannick Bolasie and James McArthur both bagged goal braces in south London.
"These players have got to come through this, but there's no one more determined than myself to do that, starting tomorrow morning. We hadn't planned the extra session.
"It's not right. We need to sort it out. You're going to do that on the training field, within the group, and within the work, and we've got to come through together.
"I'm hurting as much for the fans as ourselves. I'm really hurting.
"I've hurt in the past and we knew this was a tough job but this is getting tougher by the weeks.
"We know we're in a relegation battle, we've got 24 games left.
"It's about coming through adversity and bad times, getting stronger, showing character.
"And character, mental determination and fight - that's what you learn through adversity."
Asked if he still had the Newcastle fans' support after another drubbing, he said: "Well, I can understand that after today probably not.
"They showed their frustration, disappointment and anger, and rightly so.
"But we're as disappointed, hurt and angry as them.
"I definitely know we got a reaction from the players.
"The focus was there from the start of the game, the intent.
"But at the present moment when we get a setback we're not recovering quickly enough.
"It's definitely not ability, it's about doing the basics. It's tough, it might get tougher, but we're up for the fight."