The 23-year-old has excelled for the club since arriving from York City Knights in 2016 but as a winger, not in his preferred position.
However, with Castleford having decided not to renew veteran Jake Webster’s deal next term – the Kiwi heads to Bradford Bulls – the right centre position will be up for grabs.
Powell says they are likely to fill the void from within and Minikin – called into the England Knights squad earlier this year – is set to show what he can do.
“It will be from within the squad,” he said, when asked about Webster’s replacement.
“We’re a salary cap sport and you’ve only got so much money to spend.
“A lot of our players have improved over the last few years and that then means you’re having to pay them more money so you haven’t got a massive amount of money left.
“So that’s where developing people within your squad is massively important. Greg Minikin is a player who I think deserves an opportunity to force his way into that centre position.
“He’s come here and got in on the wing and stayed on the wing – but centre is his preferred position.”
Powell, who confirmed Samoan full-back Quentin Laulu-Togaga’e will not be at Castleford in 2019, added: “Greg’s been to see me a couple of times wanting to play centre and that’s up to him; he has got to prove that he can do it.
“But he has a lot of good qualities as a player. There are a couple of bits that he does need to improve and he’s had some injuries fixed up that will help him get some consistency next year.
“We have other options as well in terms of Alex Foster and Joe Wardle and then a couple of young guys in there that need to really strive to put pressure on.
“We won’t be going into the market place in a big way and I believe we have got a squad that’s capable and really dangerous.”
Knaresborough-born Minikin has been been missing injured recently so James Clare has taken the right-wing spot, claiming his seventh Super League try of the season in the win against Hull FC on Friday.
Minikin is in the Castleford 19 and could return tomorrow, along with Jesse Sene-Lefao but Oliver Holmes (hamstring) is ruled out.
“James Clare has come in and done a great job for us,” added Powell. “He’s really developed himself. There are some other areas that he needs to work on to get better but I think he’s surprised a lot of people this year.
“He’s got in the team, stayed in the team, been consistent and durable and done a lot of things really well. I’ve been really pleased with him.”
Meanwhile, Powell says former Sheffield Eagles star Laulu-Togaga’e will leave at the end of the season.
He arrived on a short-term deal from Halifax at the end of May to make a belated Super League debut at the age of 33 and made a series of impressive performances scoring six tries.
Castleford were initially planning to sign him up for 2019 but the unexpected arrival of talented Peter Mata’utia, the 27-year-old fellow Samoan, who joined on a long-term deal after Leigh Centurions hit financial problems, means that is no longer the case.
“Q won’t be with us next year,” said Powell.
“Again, with a salary cap sport, we made a decision and we thought about Q but we decided on a longer-term option with Peter.
“Q has been great for us and he could yet play a big part in what we’re going to do at the end of the year.
“He’s back fit now so the competition for places is great.
“I think he has got a chance (of another SL team) in particular with who’s going to come up.”
“It looks like Widnes are going to find it really tough now and teams are generally looking for quality players who can play in Super League and potentially, depending on who that is, they may have a look at him.”