The club were 200-1 to finish 1st at the start of the year given they came 12th in 2013 and have never once topped the division.
But Powell’s alchemy has proved remarkable and so, if Huddersfield Giants defeat St Helens tonight, Castleford know they will take the silverware if they beat Catalan Dragons in France tomorrow.
Asked where that would rank in his career, the 49-year-old said: “It would be right at the very top. It would be an immense achievement for us, to be honest.
“For the club and this team to be able to say they finished top would be great.
“It’s going to be a tough ask as Catalan are good at home but if we were able to do it, it would be an unbelievable achievement. The very fact we’re in this position now is testimony to all the hard work that’s gone on.
“To have the chance to finish top in the last game of the season...
“Someone said to me you could’ve asked 1,000 people at the start of the year and they’d have all said not a chance.
“I didn’t think we would. I thought we’d be top eight, but where in that I’d not considered.
“We’ll know by Saturday what the options are if we win the game – it’ll be first or second – and all we can do is look after our side of the bargain and play well.
“But whatever happens, we’ve done an outstanding job.”
Ex-Great Britain centre Powell has also, this season, led Castleford to their first Challenge Cup final in more than 20 years, a competition he won as a player with Leeds Rhinos in 1999.
They lost out to Leeds at Wembley last month but he believes that experience will aid his side ahead of the play-offs which start next week.
“I think the canvas is blank going into the play-offs,” he added, buoyed by the return of key forwards Craig Huby and Grant Millington this weekend.
“Wigan and Warrington have stepped their game up and we have in patches but we’re still looking to get a consistency to our game.
“We showed an edge for 30 minutes last week against Wakefield but that’s what we’re looking to replicate over 80 minutes.”