Why Carlos Sainz's Williams move impacts Mercedes MOST

After Ferrari confirmed that they wouldn't be retaining Carlos Sainz for 2025, the Spaniard has been hard at work in the paddock trying to secure another drive.

Discussions with Red Bull, Mercedes, Audi and Williams have all been and gone, but he decided to have commit his future to the latter with a long-term deal to join the Grove based outfit.

Team principal James Vowles has succeeded with a significant coup by securing the services of the three-time race winner, who was forced to accept that dropping lower down the grid was inevitable once Red Bull made clear their intention to sign Sergio Perez and Mercedes informed him that their priority lies with highly-rated teenager Andrea Kimi Antonelli.

READ MORE: Sainz OFFICIALLY ends contract saga with two-year deal

Despite Williams’ poor results over recent years – they have finished last in the constructors’ standings four times since 2018, ending the season no higher than seventh in that time – there are plenty of reasons for Sainz to be optimistic about his future with the Grove-based squad.

Since joining from Mercedes in time for the start of the 2023 campaign, Vowles has made significant behind-the-scenes changes at Williams, from reconfiguring key personnel and supercharging sponsorships to altering outdated systems and pushing past backmarker rivals on track in a short space of time.

BREAKING: Carlos Sainz will join the team for '25, '26 and beyond 🤩​

BIENVENIDO, CARLOS! 🤝

Read the full story ⬇️

— Williams Racing (@WilliamsRacing) July 29, 2024

Even with those positives in mind, though, Sainz will know deep down that he is taking a significant step backwards in his career. At 29, that is far from ideal.

With 2025 being the final season in which the current engine and aerodynamic regulations will remain the same, the running order on track is unlikely to change very much at all. Sainz will be well aware of this, and so will understand that the best he can likely hope for next season is sporadic appearances in the final round of qualifying and a smattering of points finishes.

But from 2026, the whole game changes. The simultaneous ripping up of both engine and aero regulations means F1 will undergo one of its biggest changes in decades. There is no telling which team will handle that revolution best.

But that doesn’t mean those on the inside of F1 can’t make well educated guesses. The engine manufacturers who will design the next generation of power units – Red Bull Powertrains/Ford, Ferrari, Mercedes, Renault, Honda, and Audi – have all been hard at work on the project for years at this stage.

Given Sainz’s final choice boiled down to Audi and Williams, his decision to opt for the latter is intriguing.

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For a long time, Sainz seemed almost certain to end up at Audi. The Volkswagen-owned brand is putting a huge amount of resource into its push into the top tier of motorsport, his former McLaren team principal Andreas Seidl is running the project, and his father Carlos Sainz Sr. has been associated with Volkswagen for many years.

And still Sainz Jr. opted instead for Williams, a non-works outfit with far less money and, in theory at least, potential than Audi.

Perhaps then Sainz’s decision can be read as a huge endorsement of the power unit which Williams will run in F1’s new era – Mercedes’.

The Silver Arrows’ works team has toiled since the current regulations were implemented in 2022, dropping further and further away from frontrunners Red Bull into a midfield outfit which seldom competes for the podium places, never mind race wins or championship titles.

The slump has been deep enough for Hamilton to be tempted away, his confidence that the team could rediscover the peak of its powers clearly having evaporated during the two seasons he has spent labouring to mediocre finishes in the middle of the pack.

Very happy to announce I'll be joining @WilliamsRacing next season! Excited about the project and the challenges ahead of us! 💪🏻

Muy contento de poder anunciar que el año que viene me uniré a @WilliamsRacing! Entusiasmado con el proyecto y con los retos que tendremos por… pic.twitter.com/oUg5IexunR

— Carlos Sainz (@Carlossainz55) July 29, 2024

But Sainz is now putting his future largely in their hands. If Mercedes can nail the regulation change, then their customer teams McLaren and Williams will benefit hugely too. If they cannot, then neither team will have a chance of competing high up the field.

It would make sense for Sainz to back the Mercedes power unit over Audi’s version. When F1’s power units last underwent a huge revamp in 2014, it was Mercedes who delivered the best rendition, completely outstripping their rivals and powering themselves into domination of an entire generation.

In comparison, Audi are not just an unknown but completely inexperienced. If Sainz has made the right bet, then his partnership with Williams could prove very fruitful indeed.

But perhaps more importantly, Mercedes could catapult themselves back to the front of the field after years of decline.

READ MORE: F1 insider reveals why Sainz's move to Red Bull fell apart

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