Piastri finished 10th place in Sunday’s season finale after an incident-filled 58-lap encounter.
After starting alongside McLaren team-mate Lando Norris on the front row, Piastri was nerfed by Max Verstappen at the opening corner.
A mistake while chasing Franco Colapinto in the laps that followed, and a resulting penalty for the impact with the Williams, further complicated his day.
Even still, the Australian saw the chequered flag on the lead lap, ensuring he ended the season having completed every lap of every race all year – the only driver to have done so.
“Pretty miserable was the first few laps,” Piastri said of his race.
“Obviously Turn 1 was what it was, and I think on the [Virtual Safety Car] restart with Franco – I need to take a look back at it – I think I just misjudged where everyone was going to brake.
“I just got it wrong, so that set me up for a pretty tough race and tough evening.”
The drama for Piastri started just metres into the race when Verstappen slithered into the side of him, pitching them both into a spin.
While the Red Bull Racing driver was able to recover comparatively quickly, Piastri was only able to rejoin at the back of the pack.
Asked what went through his mind as he was left pointing the wrong way, he said simply: “This sucks.”
“Obviously at that point I knew I needed to try and get my way back through,” he added.
“I knew it was going to be tough, but once I had come together with Colapinto, that was pretty much the nail in the coffin for my race.
“Not the best way to end off the season for myself, but for the team, couldn’t have obviously been any better.”
With Piastri out of contention at the front of the race, McLaren’s title hopes rested with Norris.
The Brit led the race from pole and controlled affairs to deliver his fourth win of the season, resisting pressure from Carlos Sainz throughout and a surprising threat from Charles Leclerc.
With the two Ferraris ready to pounce on any mistake, the McLaren pit wall wasn’t able to relax until the chequered flag.
Meanwhile, Piastri worked his way back into the points following his early dramas in a determined drive.
That included an early stop and switch onto the hard tyres, which allowed him to make progress in clean air to gain track position as others stopped.
The net result was only 10th place and a championship point as McLaren achieved its team objective, which was to secure its first constructors’ championship in 26 years.
“Very, very proud of the whole team, what we’ve been able to achieve this year,” he said.
“I’m sure it will take a little bit to sink in, as my own personal victories often take time to sink in,” he added.
“I’ve not seen many people from the team, the three or four people I have have been very happy.
“My ribs are healed up now but I might stay away from Zak in case he hugs me pretty tight!
“It’ll really start sinking in once we see everybody in the factory, you can see the smile on everyone’s face, it’ll really start to sink in.
“As drivers, obviously we have our eyes very firmly set on becoming drivers’ world champions, but it’s also very clear how much the constructors’ championship means.”
Along with bragging rights for the team, the result will likely result in prize money payments in excess of $200 million next season – more than covering the team’s racing budget as defined under F1’s cost cap.