Chase, who has put in a transfer request, was Castleford's match-winner against the club he is set to join next season.
Salford recovered from 20-6 down to lead 24-20 before England stand-off Chase transformed the game with a superb 62nd-minute solo effort that sparked a burst of three tries in four minutes.
"I had a chat with Rangi at half-time because I thought he was trying to do a little too much at times in the first half," said Powell.
"He then has a period like he had in the second half where he is unbelievably difficult to handle. Everything he did turned to gold for a 10-minute period which put us on the front foot and got us us back into a winning position.
"Rangi is special player and he certainly is if you give him any time.
"When you lose a player you gain one from somewhere and find a way to play that suits the players you've got at the time. You can't replace Rangi, you've got to play slightly differently.
"There's a lot of talk about Rangi but if he has seen fit to play somewhere else that's his prerogative. Obviously, the club will do well out of it and we've got to make sure what we end up with next season is a positive situation."
Winger Justin Carney scored three tries and Michael Channing bagged two in Castleford's third successive win.
"It looked during the first half and parts of the second that it was an end of season game that didn't mean a lot but we found enough to score some quality tries," Powell added.
"From an attacking point of view we did some smart things but we just lost our way for a period which is pretty typical of us.
"The positive thing at the moment is that we are able to grab it back and we are finding enough character to win games from tough positions. I am really pleased that we got the two points but we lack consistency and that's why we are where we are in the table.
"But there's loads of positive like there is every week."
Salford winger Jodie Broughton marked his return after a three-match injury absence by scoring three tries.
Fellow winger Danny Williams grabbed two and Marc Sneyd landed five goals from as many kicks but it was not enough to save the Reds from a fourth successive defeat.
"We just couldn't go on with the game after we took the lead," said Salford coach Brian Noble.
"Castleford had a couple of players that know how to change a game and Rangi did that for them and that's why he is the player he is.
"From our point of view I was again disappointed because we are clearly competing.
"I thought we gave Castleford too much of a leg up in the first-half and it was like a game of touch and pass at times in the second half.
"We have a good group and it is disappointing because in the last couple weeks we have been in a position to win games. We just fell off with 10 to 15 minutes to go here whereas if we'd been a bit smarter with some of our own plays it would have helped us."
When asked about Chase joining Salford, Noble would only say: "Anybody would want a player like Rangi Chase in their team wouldn't they?"
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