Beaten Grand Finalists last term, the West Yorkshire club fell short again last night after losing 14-0 in a bitterly disappointing semi-final defeat at Wigan Warriors.
Shaun Wane's Wigan side booked a spot at Old Trafford next week by utterly out-playing the error-strewn visitors whose mistake-ridden display echoed their shoddy performance when losing against Leeds Rhinos in Manchester 12 months ago.
"I'm hugely disappointed," Powell said. "We needed our boys to have their best games of the season and we didn't get that from enough players."And in the second half we panicked. There was nothing in the game; 11-0 is nothing with 20-odd minutes on the clock."I thought Wigan scrambled really well. But we were just not good enough and that’s two years on the trot that we have sat in the changing rooms at the end of the season really disappointed that you haven’t been able to do what you needed to do to win a big game, so there is clearly a mind-set change needed.
“Our pre-season needs to reflect that and I’ve been thinking about that anyway, but I thought tonight just highlighted that our mentality as a collective needs to change a little bit.
“We have got in the top-four again but when it gets down to the big games, it gets different and we aren’t good enough to win those games at the moment.
"So we have got to find a way of being able to convert that into wins and Grand Final wins.
"We're not going to be signing too many players so we've got to find a way.
"We aren’t good enough at the moment and it is as simple as that.”
The result followed on from a 26-0 loss at St Helens and Powell added: "It's two weeks on the trot we haven't scored a point.
"We made a lot of errors in both games."We've had a really good year in trying circumstances. Over the whole season we finished third in the table but it's tempered by what happened tonight."
It seems bizarre but Castleford did badly miss the control and game-management of Jake Trueman, the 19-year-old half-back who broke a hand at Saints the previous week.“His kicking game is very dangerous and for a young player, he is very calm," admitted Powell.
“Benny Roberts hasn’t played much at half-back this year and Jake was a miss for us, but injuries happen.
"He's broken his hand and if it was just that we might have risked him but he's done his scaphoid as well so we couldn't.
"We have been unlucky at times and Junior Moors was a miss as well. Hopefully we will get a bit more luck on the injury front next year.
“We aren’t going to be signing too many players and I said that to the boys so we have got to find a different way that allows us to go to places like Wigan and get over the top of the opposition.”
Wigan coach Shaun Wane admits his emotions got the better of him after watching his side provide him with the chance to bow out on the big stage.
Victory clinched a 10th Grand Final for the Warriors, with Wane now hoping to end his 30-year association with his home-town club as a champion.
"I don't cry very often but I did out there," said Wane, who will take up a role with the Scottish Rugby Union after next Saturday's clash with Warrington.
"It's emotional, it's been tough the last few weeks.
"I definitely didn't want to finish tonight, I wanted to finish next week, that's why we didn't celebrate that much tonight, the job is not done."
Wigan displayed all the defensive qualities instilled into them by Wane to snuff out the threat of the Tigers.
Scrum-half Thomas Leuluai marked his 250th appearance for the club with the opening try while full-back Sam Tomkins, one of three departing players, provided the finishing touches with a second-half try, along with a conversion, a penalty and two drop goals.
"I'm very pleased and proud," Wane added. "It was a great effort.
"We weren't great with the ball, the conditions didn't lend to that, but we showed a lot of desire with our defence against a quality team.
"There were loads of individual performances, I thought Dom Manfredi and Tommy Leuluai were fantastic."
Wigan will go into next Saturday's final, which is a repeat of the 2016 title decider which they won 12-6, on the back of a nine-match winning run but Wane says he was impressed by Warrington's 18-13 victory over St Helens in the first semi-final.
"I've a lot of respect for Warrington," he said. "I thought they were good last night. They had a good game plan and executed it. We're going to be have to be better with the ball.
"It would mean absolutely everything if I could finish off with a win. I'm very close to my players, they're my mates, and if I can do it with these group of players, it would be right up there."