Mark Webber says he is worried about Daniel Ricciardo's F1 future.
After another technical problem in Mexico, the pole sitter hinted that he would be prepared to sit out Brazil and Abu Dhabi.
Ricciardo is switching to Renault for 2019, which fellow Australian Webber described as a "strange decision".
The Red Bull driver clarified after Mexico that he will complete his last two races with the energy drink-owned team after all, but Webber admitted he has concerns about Ricciardo nonetheless.
"I think it's quite obvious he can't wait for the season to be over, which is a little bit of a concern," he told the West Australian newspaper.
"I don't want him to fall out of love with the sport."
Webber said Ricciardo's latest Red Bull troubles, coupled with the move to midfield team Renault, will test the 29-year-old's "mettle".
"He'll be questioning the sport in his head. There's not too many people to put an arm around your shoulder. Only the tough survive and he knows that," he said.
"He's got to buckle up and keep going if he wants to bounce back with Renault next year. He's made his bed over there with Renault, which I think is a weird decision, but that's what he wants to do because he wants a change of environment," Webber added.
"But it really can test how much he actually is enjoying the sport."
Some believe the conspiracy theory that Ricciardo's bad luck in the second half of the season has been because Red Bull has shut him out.
"It's always a tricky scenario," Webber explained. "It's like still living with your wife, but you are divorced."
