Red Bull Formula 1 boss Christian Horner thinks McLaren chief Zak Brown is "barking mad" for letting Fernando Alonso race at the Indianapolis 500 this year.
Alonso is skipping the Monaco Grand Prix so he can compete in IndyCar's biggest event, with his place at McLaren being taken by Jenson Button.
While Alonso's decision has created a lot of interest, Horner thinks Brown needs to see a psychiatrist for letting his driver compete at Indy.
"It is a difficult one for Fernando as he is having a tough time," said Horner in Bahrain on Friday.
Why Alonso is modern IndyCar's Mansell moment
"Zak has this problem. He has a depressed driver on his hands and he is trying to keep him motivated.
"He has come up with this idea to send him to Indianapolis, but he must be barking mad.
"It is the nuttiest race I have ever seen.
"[There is] no testing. He is just going to jump in the car. Turn 1 is a proper Turn as well, it is not easy flat all the way around.
"So I think he needs to see a psychiatrist personally."
Horner added that he would never allow his team's drivers to do what McLaren have done.
"I believe if a driver commits to a team, [doing something else] is a bit like disappearing with another girlfriend halfway through the year and then coming back," he said.
"It doesn't seem the right thing to be doing.
"Perhaps if the races didn't clash, or do it at the end of his F1 career.
"But obviously McLaren have got this approach which is perhaps different to ours, but good for them."
Williams deputy team principal Claire Williams also said that she would not have allowed her team's drivers to skip a race to compete in another event.
"I don't know whether that is because I am my father's daughter and I know Frank probably wouldn't," she said.
"But no, I don't think I would. But I won't expand on reasons why."