Pierre Gasly could lose his seat at Red Bull within the 2019 season.

That is the warning of outspoken 1997 world champion Jacques Villeneuve, following a difficult start to Frenchman Gasly's first year with the senior team.

Gasly impressed during his first full F1 season with Toro Rosso last year, and received the call-up to replace Renault-bound Daniel Ricciardo for 2019.

But the 23-year-old is struggling so far.

"I do not feel comfortable in the car," Gasly said.

"I'll have to adapt to it compared to last year's Toro Rosso, which was better suited to my driving. At the moment I feel a bit like a passenger."

For the moment he is being backed by team boss Christian Horner, but Red Bull's notoriously tough Dr Helmut Marko accused Gasly of compromising the team's winter season with damaging crashes.

"I'm sure he will eventually get on top of it," said Horner.

But if he continues to struggle, Villeneuve expects Marko's regularly-swinging axe to come down on Gasly.

"If Gasly continues like this, returning to Toro Rosso would not be a surprise," the French Canadian told Sky Italia.

"In the past, many of these boys struggled to move from a small team to a better team. People underestimate it," Villeneuve said.

"You can compare it to a driver going from Formula 2 to F1. Some can adapt more easily than others.

"Gasly will not have much luck with Marko this year," Villeneuve predicted. "We know that he is able to change his mind every five minutes."