Moyes admits he felt for the away fans after the loss.
The manager said: "I'm embarrassed for the result and the performance, and we're sorry to the supporters for it.
"There were a wee bit of mitigating circumstances – I think the midweek took a huge amount out of us. Playing Thursday and Sunday in two Premier League games, compared to [Fulham playing on] Wednesday and Sunday makes a big, big difference.
"We've had quite a bit of illness in the camp over the last few days and that's not helped.
"We allowed them to grow into the game after we started it quite well.
"I thought the first goal was a terrible goal from our point of view. We never squeezed up from the cross, which meant Jiménez could head it from eight or nine yards, rather than 14 or 15 yards.
"The ball might have gone through and out [had we done so]. We just didn't step up at all and from there things went from bad to worse. Things just turned against us really.
"I'm hugely disappointed with the manner of it.
"Even at half-time, I said 'we're not going to concede any more goals, if we're going to lose we're not going to lose by any more'.
"But what we've done in the end is that we did. There were bits of the second half where we got a wee bit closer to them and there were a couple of half-chances, and ultimately we conceded another couple of goals. It was really poor."