Steiner, who earlier this year warned McLaren risked damaging Piastri’s title chances by not backing him, now believes Max Verstappen is the “favourite” to defend his crown with four races remaining.

“His best ally to win the championship is McLaren,” Steiner said on The Red Flags Podcast.

“The ‘papaya rules’ are for Max… if they keep fighting, they keep taking each other’s points.”

Steiner’s comments came after Piastri’s fifth-place finish at the Mexico City Grand Prix last weekend, where Norris’ dominant win put him one point clear at the top of the standings.

Verstappen sits 35 points behind but has gathered momentum with a late-season resurgence.

Despite being one of Piastri’s strongest supporters, Steiner didn’t hold back in his criticism.

“It was not good enough to be world champion,” he said of Piastri’s Mexico performance.

“He’s struggling now, and I don’t know what exactly is happening, but one of the things I could conclude out of it is that… he doesn’t get support from the team to win the championship, you lose a little bit of your mojo.”

Steiner suggested McLaren’s insistence on treating its drivers equally — the so-called “papaya rules” — may have hurt Piastri’s confidence.

“I think with all these papaya rules… when they let him pass, let him go, you go, I go… in the end, I think he lost a bit of confidence,” he said.

Earlier in the season, Piastri appeared in control of the championship after four wins in five races.

But since the summer break, he’s managed just one victory and one further podium, leaving him vulnerable to both Norris and Verstappen.

“At the beginning of the season, Oscar had no pressure because he was number two in the team, unofficially obviously. Lando was there longer, he’s a lot older, he has a lot more experience,” Steiner added.

“But then I think with all the papaya rules… I think he lost a bit of confidence in races.”

1997 world champion Jacques Villeneuve offered his own theory, suggesting Piastri may have grown complacent after leading the championship for 15 rounds.

“Maybe that made Piastri complacent a bit,” Villeneuve told Sky Sports’ F1 Show.

“When all you have to fight is your team-mate, maybe you don’t push to that last limit, that last tenth of a second.”

Villeneuve said Norris’ resurgence and Verstappen’s charge have exposed the limits of Piastri’s performance.

“Lando is driving faster and better than he’s been all season. And Piastri is not stepping up. He was already at his limit,” he said.

He added that the mental strain of being beaten by a teammate can quickly spiral.

“You start doubting your way of driving,” Villeneuve said.

“You look at the data, and you say, ‘Oh, my teammate is one tenth quicker in that corner, I need to drive differently’, and that’s when it goes wrong.”

With just four races left and three drivers still in contention, Piastri faces a pivotal weekend in Brazil as he looks to silence doubts and reignite his championship fight.