Williams team boss James Vowles says he rates new signing Carlos Sainz as “one of the top four drivers – if not at times the number two driver on the grid”.

The team announced on Monday that the Spaniard, who Ferrari chose to drop after this season, would join them from 2025.

And Vowles said he was “surprised” that neither Mercedes nor Red Bull wanted Sainz next season.

“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.

“Why wouldn’t you want that in your stable?”

Sainz has won three grands prix for Ferrari and finished fifth in the drivers’ championship three times.

He has been closely matched with his team-mate Charles Leclerc since joining Ferrari in 2021, beating him in the standings in his first season, but not since.

The 29-year-old lost his Ferrari seat because the team signed Leclerc on a new, long-term contract last winter and then grabbed Lewis Hamilton after he made it clear he was open to leaving Mercedes, just months after signing a new contract with them.

Red Bull preferred to extend Sergio Perez’s contract as team-mate to Max Verstappen into 2025 and 2026, rather than take Sainz.

And Mercedes made it clear to Sainz they were not yet prepared to commit to him – they look poised to promote their 17-year-old protege Andrea Kimi Antonelli alongside George Russell in 2025.

They are also chasing Verstappen, who they believe they can prise from Red Bull for 2026, even though the Dutchman is contracted to the end of 2028.

Vowles, in his first comments to the media since Sainz’s signing, said: “Red Bull have a constructors’ championship at risk – I would have Carlos alongside Max [rather than Perez].

“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.”

Vowles said Sainz had made it clear he was committed to Williams for at least the next two seasons.

“The message that it was 2025 and 2026 and beyond did not come from us,” Vowles said. “It came from Carlos. He wanted it to be abundantly clear to all of you and the world that he is committed and this is where he wanted to be.”

Vowles moved to Williams at the start of last year after being part of the Mercedes team that won eight consecutive constructors’ titles from 2014 to 2021 and seven drivers’ championships from 2014 to 2020.

He said the fact Sainz chose Williams over manufacturer-backed teams Sauber, who will become Audi in 2026, and Alpine, owned by Renault, was “a huge, monumental decision” and “one of the proudest moments of my career”.

Williams finished seventh in the World Championship last year but have slipped to ninth after 14 races this season.

Vowles has been trying to modernise the team and this has put unexpected strains on them. He said his attempts to update the team’s construction processes had led to the car still being overweight.

Vowles, who said he first approached Sainz at the final race of last season, said: “From the beginning I gave him warts-and-all ‘here’s what’s going to happen’.

“We are going to go backwards. Here’s why. Here’s what we’re investing in. Here’s what’s coming. Here’s why I’m excited by this project, and it’s your choice if you want to be a part it.

“But I know we will have success in the future and it will cost us in the short term and I am confident that honesty and transparency has paid off.

“It was worse than I expected it to be in that there was more weight on the car, but the aerodynamic performance of the car is in a reasonable place. We just have to shed that weight off it and we can start fighting at the front.”