Lexus stole a march on its rivals when the new regulations were introduced in 2017, locking out the top six spots in the opening race at Okayama.

The Toyota-owned luxury brand went on to win both championships, with Cassidy sharing the drivers’ title with TOM'S squadmate Ryo Hirakawa.

Although Lexus ended pre-season testing on top with Cassidy himself setting the third-fastest time at Fuji, the Kiwi feels Honda and Nissan are yet to show their hand.

“To be honest, right now we are behind Nissan and Honda,” the 23-year-old told Motorsport.com. “So it’s quite a different situation to last year. It’s going to be quite tough for sure.

“I think everyone was probably hiding [their pace]. I think NISMO definitely have a lot more to come. Normally, in testing they are not so strong, but in qualifying they are. So I expect them to make a jump.”

He added: “If we do a good job, I'm sure we can still challenge for the win in the opening race. But as we saw from testing, everyone is so close to each other this year. Basically the whole field is within one second.”

No repeat of Nissan leap

After starting the 2017 season as the slowest of the three GT500 manufacturers, Nissan made massive gains on the engine side to take a dominant win in the final round.

But Cassidy feels stability in regulations will significantly reduce the scope of in-season development this year, preventing a repeat of Nissan-like leap.

“Maybe it will be a lot less, specially because the cars were new [last year],” he explained. “Basically aero-wise it looks like all manufacturers will come with a new package because during the season that is something that you can’t change.

“So everyone had to work very hard from the moment the season was over until now, there has been a massive aero development phase. And that will be locked in at the first race.”

Button a boost for Super GT

Super GT enjoys widespread popularity in Japan, with 15,000 fans turning up for the Okayama test alone, but its international fan following falls way short of other national sportscar and touring car series like NASCAR, DTM or Australian Supercars.

Cassidy hopes that Formula 1 2009 champion Jenson Button’s decision to join Super GT with the Kunimitsu Honda squad will ignite interest from fans across the globe.

“It’s awesome to have Jenson in the series,” Cassidy said. “The series is so big here. Jenson taking part will show the rest of the world how big Super GT is.

“Heikki [Kovalainen] is already here, [so is] Kazuki Nakajima, and [Kamui] Kobayashi is [also] there this year. To have four guys from F1 is really positive about the championship.”