The former England centre, 34, lines up against Leeds Rhinos this afternoon with Castleford seeking to build on Sunday’s opening day win over Warrington Wolves.
Shenton rejoined Castleford for his second spell in 2013 and has been captain ever since Powell joined the club the following year
It is unclear whether he will play on beyond the end of his current contract which finishes at the end of this season.
But Powell said: “He leaves a legacy of leadership.
“Shenny’s really grown over the period he’s been at the club in his leadership role.
“But his skill and his ability to pass the ball is, I believe, better than anyone in rugby league – across the world – in the centre position.
“The ability to get the ball to his winger is class and our left wingers score tries consistently whoever it’s been.
“He’s been outstanding for us and I know he’s looking forward to a big year. I think he’s looking great physically.”
On the feat of 400 career games – all but 58 for St Helens and 12 for England came with Castleford – Powell added: “It’s awesome.
“The way the game is played nowadays I think 400 games is incredible.
“But it’s Liam Watts’s 300th and Pete Matautia’s and Paul McShane have got 150 milestones – one for career, one for this club – so we have a 1,000 games there to celebrate.
“We’re just looking forward to it and, for those boys, we want to make sure it is a good day for them.”
Leeds started their season with a win, too, beating Wakefield Trinity.
With rugby league fans are being urged to buy ‘virtual tickets’ for this weekend’s round of Super League action in a huge fund-raising effort to support Mose Masoe, all the Rhinos’ players and coaching staff are donating £20 each to ‘pay to play’.
Former Hull KR prop Masoe suffered a career-ending and life-changing spinal injury 12 months ago.
Leeds captain Luke Gale said: “Everyone in the game has been touched by Mose’s story over the last year and he has been an inspirational figure.
“We saw first hand at the start of last year how the whole game came together to support one of our own in Rob Burrow and I know this will be no different for Mose.
“When we spoke about it as a group, all the players and staff were on board straight away and I hope Leeds fans can join in to raise as much money as possible to support Mose and his young family.”
Castleford scrum-half Danny Richardson will make his first appearance of the season.
The former St Helens player missed the victory over Wolves through injury but – with his replacement Gareth O’Brien sidelined by concussion protocols – he comes straight back in against Leeds.
Forward Jacques O’Neill (oblique) is injured so Tyla Hepi or Lewis Bienek will come in for Tigers.
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