De Vries was called up by Williams shortly before the Italian Grand Prix's FP3 session to replace Alex Albon, who was taken ill with appendicitis.
The former Formula 2 and Formula E champion immediately impressed at Monza by outqualifying Albon's regular teammate Nicholas Latifi and after a barrage of gird penalties he started eighth alongside fellow Dutchman Max Verstappen.
De Vries backed that up with a flawless performance on Sunday, keeping his position in the midfield DRS train and successfully defending his position to clinch ninth, earning two valuable points for Williams.
It emphasised De Vries' credentials to take over Latifi's seat for 2023, with Capito acknowledging he has overdelivered.
When asked by Motorsport.com if there is anything else De Vries can do to stake a claim for a seat next year, Capito replied: "No, there is nothing else he has to do. He has other commitments as well, isn't it?
"He did an absolutely outstanding job and I rate him extremely high. That's why my expectations are extremely high and he overfulfilled these.
"It's so difficult to get in that car to race for two hours and do the qualifying and not doing any mistake and not driving on its own.
"He had to defend he had attack. He had to get lapped and not doing a mistake, then he had to do the pitstop is just so complicated, and it's outstanding job."
By pointing at De Vries' existing commitments, Capito suggested that the ball is now in the 27-year-old's camp on whether he will drive for the team in 2023.
But with an Alpine seat also up for grabs, it remains to be seen whether Williams is his best possible opportunity for next year.
De Vries joked after the race that he "might need to prepare a Powerpoint" to sell his services.
"And any time you get a chance to drive a Formula 1 car it is a kind of job interview and an audition," he added.
When pressed further on De Vries' availability for 2023, Capito said: "I don't know, you have to ask him what his contractual situations are.
"You've just seen how messy it can be, and we are not known for being messy.
"I'm not doing hypothetical things, so I'm only interested in facts. If the facts are there, then there might be solutions..."
De Vries is currently contracted to Toyota's World Endurance Championship squad as a reserve driver with a view to landing a racing seat in 2023, while the 2020-21 FE champion has also been linked with a move to Maserati now his current team Mercedes is pulling out of the electric championship.
He will be on call again in three weeks' time at the Singapore Grand Prix, in case Albon hasn't sufficiently recovered from his appendicitis surgery.
On Monday Williams announced Albon suffered from respiratory failure after the procedure, with the Thai driver having to spend time in intensive care.
But with Albon set to be discharged from hospital on Tuesday, the team hopes he will be able to recover in time.
"Alex's full focus is on recovery and preparation ahead of the Singapore Grand Prix later this month," it stated on Monday.
