Piastri's fifth-place finish saw race winner Norris move one point ahead in the standings with four rounds remaining. Piastri was denied a shot at taking fourth in the race due to a virtual safety car in the last two laps.
"It wasn't so much the pace of the car because the car was pretty quick this weekend," said Piastri, who started from seventh place on the grid.
"It was more just trying to unlock it, and I felt like I've potentially made some steps in doing that today.
"Yesterday it became obvious after the (qualifying) session that there was a few things I needed to change pretty majorly in how I was driving."
The Australian dropped to ninth in a chaotic first lap, and to 11th after his first pit stop on lap 25, but battled back with a two-stop strategy that paid off.
He passed Mercedes' rookie Kimi Antonelli during his second pit stop and then moved ahead of the Italian's teammate George Russell with 10 laps remaining.
Piastri would have remained top of the standings had he managed to snatch fourth from Haas's Oliver Bearman but the virtual safety car put paid to his chances.
"Obviously when your teammate wins the race, finishing fifth is nothing that extravagant," Piastri said.
"I've just had to drive very differently the last couple of weekends, or I've not driven differently when I should have. I think that's been a little bit strange to get my head around because I've been driving exactly the same as I have all year.
"It's just the last couple of weekends the car or the tyres or something required quite a different way of driving ... I've tried to change it up a bit today and once we analyse if it's effective or not that will hopefully help see some progress."