Casey Stoner's former biggest rivals in MotoGP have reiterated their praise for the two-time premier class champion, present at the Catalunya round to complete a demo lap on Honda's RC213V-S road bike.

Stoner, who is set to return to racing at the prestigious Suzuka 8 Hours race, called time on his career at the end of the 2012 season after clinching the MotoGP crown in 2007 (Ducati) and 2011 (Honda).

Debate has raged since over whether or not the Aussie might someday return to the class - fuelled further by Stoner's offer to stand-in for the injured Dani Pedrosa earlier this year.

Honda ultimately decided against it, due to a lack of preparation time, but Movistar Yamaha's Jorge Lorenzo said he would welcome Stoner 'with open arms' if he ever decided to make a MotoGP comeback.

"For me Casey is a real natural talent. I always say that probably I never saw a better talent, a more natural talent riding a bike," said fellow double champion Lorenzo, winner of the past four MotoGP races.

"Clearly a great show to watch him riding the bike, especially around Philip Island. That was amazing. He has all my respect. For sure he will be - if he comes back someday - he will be there winning and fighting for the win.

"I also understand his decision to retire, because racing sometimes is very stressful for us and for sure it depends on your personality, or your way of living. It's hard.

"It's his decision. If he comes back I personally will receive him with open arms."

Seven-time champion and 2015 title leader Valentino Rossi said a decision by Stoner now to return wouldn't make a lot of sense given the length of time he has been out of race action.

"Stoner was without any doubt one of the best riders in MotoGP in the last years. He won championships, he won races. He was always fighting for the podium with the Ducati and with the Honda," Rossi said.

"I think we have already enough [fast riders] for this championship! Apart from the joke, yeah for sure it can be interesting [if he came back].

"But you know it's quite a lot of time that Casey doesn't race. Don't have a lot of sense that now he [would] come back.

"But will be very interesting to understand and follow the potential of Stoner with the Honda in the Suzuka 8 Hours, because also racing will be Smith and Espargaro that are MotoGP riders," he added.

"So will be interesting to understand his level of riding after a lot of time without races."

Meanwhile, former Repsol Honda team-mate Pedrosa said he had great respect for Stoner after competing against the Australian for almost his entire career.

"Well he's been in the pit box, around, and I've been talking to him and he looks quite comfortable in his situation," Pedrosa said.

"Of course to watch him ride and to be at the time one of his rivals it's a great pleasure. If I remember now, I've been racing with him since we were 15. Huge respect.

"I really enjoy when he comes over and have some chat because he's been a great rider and always you can learn something from his experience and character.

"Of course watching him ride is special and we'll see him ride in the 8 Hours. So I hope he enjoys that and here in MotoGP it's hard to say," Pedrosa added.

"The will and the desire is the most important to be racing in MotoGP."

Stoner, whose most recent Honda MotoGP test was at Sepang in January, will team up with Michael van der Mark and Takumi Takahashi for next month's Suzuka 8 Hours.

Britain's Bradley Smith, who will be up against Stoner at Suzuka, will have two tests at the Japanese circuit after the MotoGP rounds at Assen and Sachsenring.

"We've got to do two tests at Suzuka. One after Assen, one after Sachsenring. So that will give us a good indication of what we need to do [fitness wise]," he said.

"I'm taking my doctor and my whole programme over there ready for that event. It's obviously important to prepare for it, especially the heat.

"So pre-cooling, post-cooling. That type of thing. But nothing different to what we have in MotoGP."

Smith's urge to compete at the event is fuelled by his love of the circuit, which he says is held in the same esteem as venues such as Mugello in Italy.

"Mainly a love of the track, or people's love for the track," said Smith, asked why he has a desire to race at Suzuka.

"People speak about Suzuka in the same way that they speak about Mugello. It's that type of flowing track that's so fun to ride. Also Phillip Island.

"Basically it was more the fact of 'how am I going to get a chance to ride Suzuka?' and it was the 8 Hour.

"There's also the physical challenge and the chance to do it on a Factory bike - it sounds pretty good!"