The Super League leaders showed their class once more with a 29-18 triumph against their derby rivals in Newcastle.
However, they were level 6-6 at the break before Greg Eden’s second-half hat-trick saw them seal a sixth straight win over Leeds.
“I thought we were a bit unlucky in the first half,” said Powell. “The boys were quiet at half-time. We just needed a bit more composure and we changed the way we were playing a bit in yardage. Paul McShane was superb, controlling the middle throughout the second half and that got us the ascendancy.
“I thought he won us the energy battle. We kicked the ball really well and there were some great pieces of skill and class from our left-edge in particular.
“Overall it was a perfect game for us, being really challenged and having to dig our way out of it.
“The whole of the 17 played really well.”
Leeds coach Brian McDermott was encouraged despite the defeat and took plenty of positives especially after they had lost 66-10 the last time they met.
“It was a great contest and we stuck with Castleford,” he said.
“But just after half-time we lacked concentration and composure and flaked out a little bit, unfortunately, both with some defensive errors and with the ball.”
He confirmed former England winger Tom Briscoe, who was taken off in the first half, was not injured.
“He came up with too many errors,” said McDermott.
“He is a good player and has been good value for us this year, but in a game as important as that you can’t make so many errors.”
“That’s not normally us, but that’s what a team that applies pressure looks like. Castleford executed and put some of those plays on that we know they are going to do. They are a good team, Cas, but we were in the fight. I thought we were good value.”