The England international has been impressed with the West Yorkshire club this year given the manner in which they have raced to top spot.
Castleford, who visit the defending champions tomorrow, are currently 12 points clear of nearest rivals Leeds Rhinos and set to finish by a record margin.
However, as they seek a maiden Grand Final appearance and first-ever title, Tomkins wonders if they can repeat their quality when it matters most having lost a Challenge Cup quarter-final at Hull FC earlier in the campaign.
“They’ve been the most consistent side all year and got the League Leaders for it,” he said.
“The challenge for them is to win a knock-out game, because they’ve only been involved in one big one and they came up short.”
Furthermore, Tomkins does not understand why so many people have eulogised about Castleford’s free-flowing football in 2017.
Daryl Powell’s side have swept past so many opponents, averaging 32 points per game while playing with real panache.
But, ahead of a game under-pressure Wigan ideally need to win in their own race for the top-four, he feels their style is nothing new.
“They’ve been the best side this year; they’ve been consistently good, and we know it’s a massive challenge,” said Tomkins.
“I heard an interview with Michael Shenton, I think it was him saying they’re changed the way rugby league has been played – or he was quoted saying that –and they’re not doing that.
“They’re playing well. But they’re playing similar shapes to what every team plays.
“In 2010, when we started doing block plays, we were running different shapes which people hadn’t seen before. But all teams now run very similar set-ups and whichever runs it best comes up with the goods.”
Tomkins missed Wigan’s two games against Castleford in April – Warriors lost both times – due to a problematic broken foot that sidelined him for much of this campaign.
He was duly omitted from England’s elite training squad ahead of the World Cup which starts at the end of next month after struggling for form but Wigan coach Shaun Wane feels he has done enough since to earn a recall.
However, Castleford’s own Zak Hardaker is deemed the favourite to take the No1 jersey, placing extra emphasis on their battle tomorrow.
Tomkins, 28, said: “Zak’s been outstanding this year; he’ll want to play for England and so do I.
“Being up against Zak, he’s been playing some of his best rugby so I need to test myself.”
Wane added; “Cas’ have been the most consistent team and quite rightly won the League Leaders’. But the one sudden-death game they played, the main one, they got beat.
“Hull found a way to get the win, and we need to do that. They’re a hard team to break down, no question.
“We want the points but our motivating factor is they’ve not seen anywhere near the best of us. I want us to perform.”