They play their final Super League game at Wigan Warriors having seen their hopes of finishing in the semi-final spots extinguished more than a fortnight ago.
However, Powell – whose squad came fourth last year – feels they have to make steps now to demonstrate they are here to stay as a genuine force in the elite.
They impressed by winning at leaders Leeds Rhinos for a second time this season last Thursday and Powell wants a repeat performance against a side who are firmly in the hunt for the League Leaders’ Shield heading into the final 80 minutes of the Super 8s.
“It may seem we’ve nothing to play for but we have,” said Powell. “This is us looking to make that change to a top-four team now – not waiting until next year.
“I spelt that out to our players a couple of weeks ago when we lost to Saints. I said: ‘Right, here we go, we need to flip our mentality.’
“I thought we did that last week at Leeds and this is us now going on with it, rubber-stamping that we are a top-four side.
“Wigan are fighting for the top of the pile. We know they will be highly motivated but I told our guys this is a key game for us.”
Castleford have confirmed Ashley Gibson, Michael Channing – both in the 19-man squad tonight – and England Academy player Brandon Moore will not be retained for 2016.
On Wigan, Powell added: “They have been really tough at home.
“They are unbeaten there apart from against Brisbane in the World Club Series and Hull KR in the Challenge Cup.
“Their season completely flipped – their home form’s been unbelievable but their away form is, well ... they’d be the first to say pretty average.
“They’d be disappointed with that. We played them at home (42-14 in March) and were way too good for them.
“They will be bristling this week based on what’s in front of them.
“Wigan don’t like to get beat and see it as a real challenge the next time they face sides who have defeated them.”