Ahead of a first-of-its kind crossover race between the two series, GT500 manufacturers Honda, Nissan and Lexus will send one car each to Germany to compete in the DTM finale.

Ex-Formula 1 driver Button will represent Honda at the event, driving the Kunimitsu NSX-GT with which he won the 2018 GT500 title with Naoki Yamamoto.

Although both series share several common parts ahead ahead of a full unification to Class One rules next year, Button is unsure how closely matched the two types of cars will be after BoP adjustments are put in place.

The Englishman pointed out that SUPER GT drivers will have to make a number of changes to adapt themselves to DTM-style of racing, with Hankook tyres, tyre change-only pitstops and standing starts some of the major pressing points in his opinion.

“It’s very difficult to know what to expect because I think Super GT has a bit more power and a bit more downforce,” Button told Motorsport.com.

“But the benefits the DTM has, they have DRS, push to pass and they know the tyres, we don’t the tyres. I have never driven the Hankooks. It’s all going to be new. So there are many different variables.

“Also pit stops on the Hankooks. For us they take 30-40 seconds because we refuel, driver change, tyres, for them it’s 7 seconds.

“Also the starts - they have standing starts, we have rolling starts. So something else to learn. Hopefully the cars are close enough so we can race, have fun.”

Button’s uncertainty over the competitiveness of SUPER GT cars was echoed by Nick Cassidy, who will share the TOM’S Lexus car with Ryo Hirakawa.

The race will mark Cassidy’s second European outing of 2019, after his Spa 24 Hours appearance at the wheel of a HubAuto Corsa Ferrari 488 GT3.

“Yeah, I’m not sure,” Cassidy told Motorsport.com. “I’m really excited I must say about going to the race. I’ve always been a huge fan of DTM.

“I think it’s a great championship, really strong drivers, strong and amazing manufacturers. So it’s really exciting thing to be part of that.

“In terms of performance and things, in the end I think the series, both SUPER GT and DTM, have a fairly big control on that. It’s more up to them and how they decide for us to perform.”

“We are the only Lexus so same situation for Jenson and I guess Ronnie [Quintarelli and Tsugoi Matsuda of Nissan]. Our cars won’t be matched I think too closely because it will be the first race event.

“The focus should not be on the driver, but more the focus I think on the combination of the two series and trying to develop that for the future, which I think is the main thing and quite important.”

Button, however, remains excited by the prospect of the SUPER GT and DTM sharing the same track - especially as the two events at Hockenheim and Fuji mark the culmination of a collaboration that began several years ago.

“It should be fun,” he said. “I really like Hockenheim, it’s a good circuit for racing. Also to race against the Audis and BMWs, it should be a good experience

“It’s very unusual for cars from one category to go and race in another category. So I think it’s very cool.

“Whether that actually leads to anything in the future, I don’t know. You know maybe there will be one or two races every year but I still think that SUPER GT and DTM will have their own individual championships.

“But this is a fun experience. while I’m racing in SUPER GT, it’s nice to go and race with DTM and against DTM.”