Tony Gigot, who scored a hat-trick of tries, and Todd Carney inspired the Dragons as they claimed a resounding home victory, despite losing Ben Pomeroy to his second red card of the month.
Pomeroy saw red for a dangerous throw on Ashley Gibson.
Castleford shipped 11 penalties and Powell accepted his visitors were their own worst enemies.
Powell said of the Tigers display: “We had such a poor start and had too many people off (their game). Catalans were excellent and fully deserved to be 20-0 in front before we even looked like scoring.
“Performance-wise we were really off. Catalans played some good rugby from the start and really put us on the back foot from the start.
“If you don’t get a good start here then it is always tough. I still thought we could win at half-time. It was obviously tough for both sides today with them having a man sent off and us losing players through injuries.”
Veteran Australian coach Brian Smith admits keeping Wakefield Trinity Wildcats in Super League would rank among the most satisfying achievements of his distinguished career.
The former Parramatta, Sydney Roosters and St George Illawarra coach, who changed the fortunes of Hull and Bradford the last time he worked in England, was brought in by Wildcats chairman Michael Carter in May with a brief to keep the strugglers in the top flight. Back-to-back wins over leading Championship clubs Bradford and Leigh have put him on course to do just that.
There was little to choose from in Saturday’s game against Leigh, with full-back Lee Smith’s 69th-minute drop goal separating the teams, but a 17-16 victory boosts the chances of Smith’s men securing a top-four finish in the Super 8s Qualifiers.
“From a satisfaction point of view, I think it will probably be right up there, it will be for everybody in our club if we can manage that because I don’t think we could get much lower than Wakey was during that long run of losses,” said Smith, who managed to halt a run of 16 straight Super League defeats in July.
“The spirit and desire was still there to do something about it and we saw that again.”