The Super League leaders almost became the second high-profile victims for Rick Stone’s side who had won at Leeds Rhinos the week before,
But, despite trailing in a second period largely dominated by lowly Huddersfield, Castleford struck via Jesse Sene-Lefao’s 74th-minute try to go three points clear at the top.
“For attitude, commitment and digging our way out of a hole, it was a great win,” said Powell, who had to make a raft of changes with three England players missing.
“We had another combination in the halves when Rangi (Chase) went off and things didn’t go as we’d have liked.
“But for guts and determination – and the amount of times we kept them out on our try line – this was a big win for us.
“It’s the first tight game we’ve won this year. Most games we’ve won pretty convincingly.”
Powell had issues with Jake Webster’s yellow card for a ball steal that saw the Castleford centre sin-binned and saw Danny Brough put Huddersfield 21-20 ahead.
“It was a poor call; the tackle was never complete and it looked like it was going to cost us.”
However, Huddersfield coach Stone also had complaints about Ben Thaler after the referee then sin-binned Brough for an alleged ‘cannonball’ tackle that led to Castleford gaining position to win.
“There was a few issues I’ll be raising with the refs’ boss this week,” he said.
“I thought Castleford could have had a man off for a tackle in the air on Darnell McIntosh, too.
“I’m really proud of the effort. We had a lot of players missing as well.”
Justin Holbrook has been appointed as St Helens’ new head coach.
Holbrook, 41, will leave his current job as assistant coach with the Sydney Roosters to succeed Keiron Cunningham at the Totally Wicked Stadium.
The announcement was initially made by the Roosters, with head coach Trent Robinson saying: “This is an exciting opportunity for Justin and on behalf of everyone involved with the Roosters, we wish Justin, his wife Nat and their young family all the very best.”
Holbrook, who also coaches the Junior Kangaroos, has signed a two-and-a-half-year contract.