Williams boss James Vowles was surprised neither Red Bull nor Mercedes showed serious interest in Carlos Sainz for 2025 and beyond.
Sainz, set to be replaced at Ferrari by Lewis Hamilton, will join Williams on a multiyear deal next season.
The deal ended months of speculation about his future, but during a Tuesday media call, Vowles said his interest in Sainz stretched back even further, to last December and the 2023 season-ending race.
"There's only one driver team I spoke to in Abu Dhabi last year, only one, and it was Carlos," Vowles said. "Just to be super clear on that. I didn't spread bet. I went for one driver that I thought would make the difference."
When the Hamilton-Ferrari news was announced on Feb. 1 of this year, Sainz was initially seen as a candidate to replace the seven-time world champion at Mercedes, but team boss Toto Wolff never showed a serious interest.
Vowles, who joined Williams from Mercedes in 2022, said he had no prior knowledge of Hamilton's move but saw Sainz as the best option for Williams to chase.
Sainz also explored a return to Red Bull, sensing an opening either as Sergio Pérez's replacement in 2025 or if Wolff was able to successfully tempt Max Verstappen over to Mercedes for next year or the year after.
But the Red Bull option also never looked serious, with the world champions extending Perez for another season earlier this year.
Asked if he was surprised big teams overlooked Sainz, Vowles said: "Yes, is the short answer to it, because I rate him as 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?
"Because my view of things is fundamentally competitors are getting closer and closer so the marginal difference the driver can make... and I don't just mean in performance terms, look at Carlos and look at every team he has been in, they have improved significantly."
Red Bull confirmed this week Perez will remain at the team beyond the summer break, despite his poor recent form, while Mercedes seem set on elevating Formula Two teenage rookie sensation Andrea Kimi Antonelli for next season.
Vowles said both teams know the reasons for their own decisions but felt a driver of Sainz's calibre could have helped them both.
"What I've realised with him is Carlos is a performance machine. He absolutely will do everything it takes within his power to not transform just himself but the team around him at the same time. And that's powerful, that's worth more than what he can drive the car at, that's worth that you move the team forward at the same amount," he said.
"So when you're in Red Bull's position when you've got a constructors' championship at risk, it's always a hard decision but yes, I would have Carlos alongside Max.
"If you're at Mercedes, it's a hard choice, they've swayed between not being competitive, in which case it makes sense to invest in the future, to being very competitive ... now it's a harder decision as to whether you invest in known entities or unknown.
"But that said if Mercedes have made that decision, they have far more information than I do, it's more than likely they're confident in the direction of travel they'll be travelling in -- whether that be Max or Kimi, I'm unsure, but my point is they're not fools, they've made the decision sensibly.
"And if Red Bull have decided to do this, again, there's reasons behind it I won't be aware of, they're multiple world champions and they don't take decisions lightly. But I was surprised, to answer the question."