Huddersfield coach Paul Anderson said the Giants were down on energy and were beaten by the better team last night.
Castleford defeated the Giants 22-30 at John Smith’s Stadium.
Anderson said his side struggled with a short turnaround from Sunday against Widnes.
“I tip my hat to them, I thought Cas were the better team,” he said.
“I didn’t think we were great tonight. Defensively we weren’t great today. Some boys were running on empty out there tonight.
“I just said to the boys, we can’t gloss over the fact that we weren’t great. We’ve still got to be better than that.
“We looked a team that was real down on energy.”
Huddersfield remain in 11th place, just two points above 12th placed Leeds.
“It is what it is,” Anderson said.
“We’ve got some mountains to climb. They’re a good team Cas. I hope they do well.”