The 20-year-old was outstanding, also creating another two tries, as they destroyed Hull FC 44-12 at Wheldon Road.
Trueman’s epic display came just days after being named in the Great Britain squad and left his coach - a former Lions No6 himself - purring.
“He’s just fantastic isn't he?” said Powell, as Castleford replaced Hull in fifth with just one game to go.
“The boys call him World Class. And I think he’s every chance of being that for a long time to come.
“Some of the things he does are so instinctive. He has a cheekiness about his game, too.
“We had a bit of a moment in a meeting this week where Jesse (Sene-Lefao) said ‘I’ll look after Truey defensively’ as they have some big back-rows.
“But he said ‘I’ll look after you!’ He’s just so strong
“Truey’s so unassuming and he’s old school as well. I just love watching him play.
“But it was a great performance all-around by the lads. That opening 30 minutes was outstanding.”
Castleford were 20-0 up inside just 22 minutes against opponents who would have secured their own play-offs place with victory.
Tigers nailed a fifth victory in seven Super League games and could go under the radar as they seek to repeat their feat of reaching the Grand Final two years ago.
They will confirm the fifth and final spot if they avoid defeat at Wigan next Friday.
Even if they lose they will qualify if freefalling Hull - who had been in the top-five since March - also lose at home to leaders St Helens.
Powell said: "We showed we really wanted to win the game.
"Defensively we're so much better and attitude-wise we're in a great place.
“We know we're outsiders but it doesn't really matter to us.
"We're playing with confidence and without fear, and it's helpful when you can do that.
"We've been talking for the last three weeks about being in play-off mode now and that's helped us.
"We're in a great place. We've got to go to Wigan next week which is always a tough battle.
"Everybody said we had a tough run-in but it's been perfect, it couldn't be any better.
"If we're going to be in the five then we're going to be good enough. And if we are in the five and we're good enough, we'll be a challenge for everybody."