Sargeant has endured a difficult debut season with Williams, showing flashes of promise that were punctuated by rookie mistakes in his ambitious quest to try and get on par with a high-flying Alex Albon.
While some errors led to headline-grabbing crashes, others flew under the radar but cost the Floridian a better qualifying position, putting him on the backfoot - and left him without points until last month's US Grand Prix.
But, in recent weeks, Sargeant has shown a much steadier approach, which he was able to convert into seventh place on the grid on a Las Vegas street circuit that suited the efficient Williams much better than the preceding events.
In Q2 and Q3 he stayed within two tenths of Albon, who will start one place ahead, after being a tenth quicker in Q1.
Speaking to Autosport, Vowles said he hopes Sargeant's seventh place, which will become sixth on the grid after Carlos Sainz's penalty, can be a turning point regardless of the outcome of Saturday's race.
"I hope so - I think certainly, when you score your first point, it creates a turning point for you," he said.
"When you start performing against your team-mate that is one of the best in the world and be within a few tenths, and against everyone else on the grid, then you find another turning point.
"This gives you the confidence to know that you have the ability required."
Vowles had specifically tasked Sargeant with doing a better job in balancing risk versus reward rather than trying to overdeliver, which he feels the 22-year-old has been able to achieve.
"One of the most important things is having the confidence that you deserve your place within the top 20 of best drivers in the world and deliver lap after lap. And he did that today," he explained.
"There's a few reasons why. First of all, at every track we've gone to this year someone has done laps before. It's the first time here, so you can remove his rookie status. No one's done a single lap around here.
"The second is that he's really matured over the last few races. You can see there are no mistakes, just clean execution and build-up across the weekend.
"This weekend is an exact example of that as well, he just built it up and started pushing the risk factor more and more."
Vowles added: "He's doing an incredible job and it's hard probably to explain to the world how good a job he is doing.
"It's taken a year to get there, but you're now seeing the result of that and the dividends are paying off."
Sargeant's relief at finally putting his car on the grid position it deserves was evident from his joyous outburst on the team radio, and he was still beaming when asked if this was his best weekend performance in F1 so far.
"So far, absolutely," Sargeant replied. "It means a lot after putting so much hard work into trying to be able to do these things. And it's very irritating when in the past rounds you see that potential, but you don't do it.
"I don't think we could have done a whole lot more today, so hats off to everyone in the team. We knew this weekend was a good opportunity. And we're off to the right start."
Additional reporting by Mandy Curi
