Toto Wolff said Mercedes’ worst performance on his watch as team principal shows they are right to make wholesale design changes for next season.

Lewis Hamilton finished eighth at Sunday’s Brazilian Grand Prix – more than a minute behind race winner Max Verstappen – while George Russell retired with an engine failure while running in 11th.

Far from being any closer to Verstappen’s all-conquering Red Bull, Mercedes were slower than McLaren, Aston Martin, Ferrari and the mid-table Alpine team in Sao Paulo, with Pierre Gasly embarrassing the former world champions when he batted Hamilton and Russell aside.

“It is totally baffling and unacceptable,” said a beleaguered Wolff.

“We are a proper structure, a solid team but that didn’t look like a solid team today. For me personally, it was the worst weekend in 13 years (in Formula One).

“The development of that car has been about putting plasters on something that was not right and it shows that it is so unpredictable that it can swing either side.

“Fundamentally, we will have a different car next year and today proves that is the right thing to do.

“It feels horrible for the whole team. And I wish we could start the new season concentrating on the new car.”

Performances at the previous two rounds had afforded Hamilton and Mercedes hope that they were closing the gap to Red Bull.

Armed with a new floor in Austin two weeks ago, Hamilton finished second before he was disqualified after his Mercedes failed a post-race scrutineering check. He was runner-up again in Mexico seven days later, this time with a legal car, 14 sec adrift of Verstappen.

But the Silver Arrows were dealt a grizzly reality check at Interlagos – a venue where they expected to perform well after Russell claimed Mercedes’ sole victory there last season.

Wolff continued: “It’s baffling. From having a really quick and balanced car and drivers really happy, to a nightmare. How is that possible?

“I wouldn’t be surprised if we analyse the cars in the next few days and we find out that there is a mechanical issue in the way we set them up.”

Russell was forced to park his machine with 12 laps remaining but the Englishman hopes Mercedes’ abysmal performance was track specific – with rounds to follow in Las Vegas in a fortnight before the concluding race in Abu Dhabi on November 26.

“It was a mind-boggling weekend to understand,” said Russell. “We had high expectations heading into this weekend and we had absolutely no pace at all.

“There are so many question marks. It is the same car that we have had for the last five races which has been capable of podiums.

“This is clearly a substantial one-off event, but we need to understand what we got wrong because right now, we don’t really know.”