The Rangers boss could only watch on as his side were dismantled at Craven Cottage after a 'nightmare 48 hours' where they lost players to injury
Martin Jol's side took the three points courtesy of an Andrew Johnson hat-trick, as well as goals from captain Danny Murphy, Bobby Zamora and Clint Dempsey.
"I think I've had a couple of these before," Warnock told reporters. "They're not easy anyhow, it's one of the worst. But if ever there was a day to catch us it was today.
"Good players take advantage of the situation, and the last 48 hours we've had a nightmare really what with [Danny] Gabbidon's injury recurrence, and we've lost [Matthew] Connolly yesterday through an innocuous challenge with Shaun Wright-Phillips in training.
"Then we had Fitz Hall, who had an injury in the warm-up today," he continued. "Then we've got [Armand] Traore who's sitting in the stands today but it shows that we can't cater with the squad we've got."
"I'm learning though," Warnock added. "We've got to look after ourselves until January at least because things can happen like this. You can lose four players in the space of a few hours, and we can't cope with that really.
And with his side denied of their first choice defence, Warnocked conceded the ease in which Fulham were able to punish his side, giving Jol's men credit in the process.
"I thought it was like a knife slicing through butter today," bemoaned Warnock. "All credit to Fulham, they took advantage, and all good players will take advantage of a back four in disarray really. I don't think anyone packed up or anything, I just feel that on the day they were too good for us really.
"We've done well so far, building from the back with a few clean sheets which is fabulous, but we can't afford too many injuries. I think most teams would have beaten us easily with the way we defended.
"We had to chop and change really. We had Luke Young playing at left-back, Bradley Orr coming in and Fitz Hall had to play really. So it was disappointing to lose when you look at the back four who have got the clean sheets, it's Traore, Gabbidon and Luke Young at right-back.
"I don't think we're good enough yet to lose three players like that and not get punished. Although in fairness I thought we could have had a go after half-time and restore some pride, but to lose a goal like the fourth one is very disappointing to say the least. That's Sunday league stuff, isn't it.
"I don't think we should talk about individuals today, because they were all pretty bad. We've had a bad day at the office today. But that's what you're going to get. You're going to get some drubbings, but to be honest with you I didn't expect one today."
Warnock did however, note his appreciation of the display from the away fans who he says appreciate the journey they have been on.
"The fans today were fantastic; they know how far we've come and how quickly we've done it. You know you're going to get some days like this in the Premier League, it's a cruel league with some good players but we do know we have to be at our very best every game to play at this level."
And Warnock also spoke about his mercurial winger Adel Taraabt, who he substituted at half-time after a disappointing first-half display.
"I don't think you can blame Adel Taraabt for today. I think if we had Darren Bent and a few England players out there we probably still would have got beaten 6-0.
"You're going to get a few days where Adel comes off and throws his dolls out the pram, but that isn't a worry for me. If I sub someone and they are happy, that's a more worrying sign for me."
There was, however, one bright moment for the visiting fans, who got to see striker Jamie Mackie make his comeback from injury after a leg break last season.
"It was great for [Jamie Mackie]. I wanted to give him 15 minutes because he's had so many knockbacks in the nine months since he broke his leg. He's been told 'next week you'll be back with the squad' and then three weeks later or four weeks later you're not there and it can get to you.
"You've seen today, he doesn't know any other way and I'm pleased for him. At least it's one little bright point for the fans today because they know how important he was for us last year to get where we are now."