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.
Source: Autosport