Williams team boss James Vowles admitted he was surprised that neither Red Bull nor Mercedes wanted to sign Carlos Sainz for the 2025 season.

The Spaniard signed a two-year contract with the option to extend at Williams earlier this week, ending speculation surrounding his future.

Ferrari had confirmed earlier this year that he would not continue with them past the end of the season, having signed Lewis Hamilton from Mercedes to partner Charles Leclerc.

While Sainz was initially seen as a candidate to replace Hamilton, Mercedes look set to promote 17-year-old Andrea Kimi Antonelli instead, while Red Bull preferred to extend Sergio Perez's contract for the next two years.

Vowles was full of praise for the 29-year-old, explaining how it was an easy choice to bring him into the team.

"Look at Carlos," said Vowles. "Look at every team he has been in. They have improved significantly - and I get why.

"After spending the last nine months talking to him at least weekly, what I've realised is he is a performance machine.

"He will do everything in his power to transform himself and the team around him. And that's powerful. That's worth more than what he can drive the car at.

[He is] one of the top four drivers - if not at times the number two driver on the grid. Why wouldn't you want that in your stable?"

Sainz has achieved three Formula 1 wins to date, including a victory at the Australian Grand Prix in March, and currently sits fifth in the drivers' championship.

He is only 15 points behind team-mate Leclerc, who sits in third, while his five podium finishes this season have also helped Ferrari to third in the constructors' championship, where they sit 63 points behind leaders Red Bull.

There is speculation that Mercedes could make a swoop for Max Verstappen for the 2026 season, despite his Red Bull contract running until 2028.

With so many F1 futures up in the air, Vowles was surprised to find out there was not more interest in their new driver.

"Red Bull have a constructors' championship at risk - I would have Carlos alongside Max [rather than Perez]," he added.

"Mercedes have more info than I do. It's more than likely that they are very confident in the direction they will be travelling in. Whether that will be Max or Kimi, I'm unsure - but they're not fools.

"Red Bull will also have reasons behind it that I won't be aware of because they are multiple world champions. They don't make decisions lightly, but I was surprised."

Lewis Hamilton would choose Andrea Kimi Antonelli to take his Mercedes seat when he makes the move to Ferrari next year.

In February, Hamilton stunned the Formula One world by announcing he was exercising a break clause in his contract with the Silver Arrows and would join Ferrari from 2025. 

Several drivers have been linked with the upcoming vacancy at Mercedes, including world champion Max Verstappen, though he is thought likely to stay with Red Bull for next season.

Carlos Sainz – who will lose his Ferrari seat to Hamilton – has also been tipped as a potential candidate, but Hamilton thinks 17-year-old prodigy Antonelli deserves a chance.

"Carlos is a great driver, so wherever he goes I think he would be a positive for any team," Hamilton said of Sainz. 

"Honestly, I have no idea what Toto [Wolff]'s plans are, but for me, taking on a youngster, I would probably take on Kimi."

Antonelli has been part of Mercedes' junior team since 2019 and currently competes for Prema Racing in Formula Two, sitting sixth in the drivers' championship standings after four rounds of the 2024 season.

Speaking at Sunday's Emilia Romagna Grand Prix, team principal Wolff hinted the teenager was under serious consideration for next year.

"I guess for the Italians it's super exciting to have Lewis Hamilton in red next year. We will get used to the outfits, but we have got to look at ourselves," he said.

"Maybe there is an option where we can shine more with an Italian in our car, so we're pushing back hard."