Fernando Alonso's fellow Formula 1 drivers say they would not skip a grand prix to race elsewhere, as he will do to compete in this year's Indianapolis 500.
The McLaren driver will race at Indy instead of competing in the Monaco Grand Prix, and it was the fact he will miss a race that came as the biggest surprise to other drivers on the F1 grid.
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Lewis Hamilton said he would never miss an F1 race to do something else, while Nico Hulkenberg, who won the Le Mans 24 Hours in 2015 with Porsche, said his situation had little in common with Alonso's.
"In my case it was completely different, I didn't go away from F1 in the way that he does," said Hulkenberg.
"I would never have done it if I had to miss a race for it, especially Monaco.
"I am a bit surprised, like everybody, about this situation."
Hulkenberg also said he had more time to prepare for Le Mans than Alonso has for the Indy 500.
"I don't know much about Indy, but he has never driven these cars on ovals," he added.
"You think you can just come in and win that easy? I at least had half a year practice and leading-up time.
"It sounds like a big challenge, but Fernando likes a challenge."
Romain Grosjean, who has expressed an interest in entering a NASCAR race as his Haas team competes there too, said he is too committed to F1 to consider doing Alonso has chosen.
"I wouldn't do it - I give 100%, I push really hard, I'm here to do the best for the team," said Grosjean.
"I really would like to do a NASCAR race, but being part of a project, especially like Haas or like Honda in Formula 1 and developing everything, making sure the team arrives to the top level, is something more important.
"I'm surprised he can skip a race and say 'I'm going to do another race'.
"It's great for motorsport having a driver from Formula 1 going to Indianapolis, but you can do that when you've finished.
"I don't know how it looks from the outside, I'm just saying I wouldn't do it if I was committed."
Alonso's former Ferrari team-mate Felipe Massa added: "If you decide to do a race like Nico did, racing at Le Mans because it's not the same weekend [as F1], everybody would not be so surprised.
"But changing a race in Formula 1 to do a race in another category is definitely a big surprise."
While Sergio Perez agreed he "wouldn't miss Monaco, it's my favourite weekend of the year", he did make clear he would love to compete elsewhere alongside F1.
"I would like to do some other races, I have an interest in IndyCar, and the Indy 500 is one of the biggest races of the year," said the Force India driver.