The Grove outfit has been widely tipped to take Alpine youngster Oscar Piastri on a loan deal next season as replacement for Nicholas Latifi.
However, the team's own protege Sargeant has enjoyed a recent surge in form, winning the F2 feature races in both Britain and Austria, as well as finishing second in Baku.
The American lost some momentum with a frustrating weekend in France after earning his second pole of the season, but he still lies third in the championship, 55 points behind Felipe Drugovich.
Should he ultimately win the title, he won't be able to continue in the category in 2023, leaving Williams to find a new role for him.
"It would be a great headache, wouldn't it?," said Capito when asked about Sargeant's prospects.
"I've had worse ones. Of course, we are impressed. You know, it's his first season in F2. We didn't put any pressure on him. So he has the time to develop, and he's really impressed us with how fast he has got to grips with the car, about the tyre management and getting results.
"How he got the pole [in France] was really impressive. He will be in an F1 car in the future, I'm absolutely convinced."
Capito stressed that it was too early to make plans for Sargeant.
"For example, he needs the superlicence points. And for that he has to finish in the top five in the championship. In the moment, it looks good.
"But you know, you can always get the other way pretty quickly. So it's quite tricky to take early decisions on something on a F2 driver as long as the season is not over. So that's part of the decision making, of course."
Williams has already deployed one of its rookie FP1 slots this year, with Nyck de Vries driving in Spain, and Capito indicated that Sargeant has already earned a slot.
"I think that would be obvious. We haven't announced yet. Our young driver academy is working very well. We had three good results recently. Logan won the last two races and he set the car on pole [in France], so I think he deserves to get into the car."
Capito also indicated that Williams would be willing to take another team's driver on loan – such as Piastri – but only if it was the optimum overall choice.
"I think if that was the best for us, then we would consider that. If it's not the best, if we have another, better solution, we will go for the better solution.
"I think we've got various options. And that's the options we are thinking about as well. And we will finally go for what we believe is the best for the team. But it's too early to get into details, because we're not there yet."
