Piastri endured the most difficult day of any driver in Formula One's season-opening grand prix, failing to make the grid after crashing out on his reconnaissance lap.
The incident marked the first time the 24-year-old had done so in his career, with the crash coming in front of a record crowd in his hometown of Melbourne.
"Oscar, very unfortunate. Definitely a tough moment for him in front of the Australian crowd," team principal Andrea Stella said.
"But he is a very tough guy mentally, he will use all of this to get even more concentrated and determined starting from China.
"We will make sure we will face this in a united way. We are a team in any situation that may involve anybody in our team."
McLaren are investigating the full details of Piastri's crash ahead of next week's Chinese Grand Prix, but believe a surge in torque combined with cold tyres prompted the issue.
There is also a thought that the sport's new regulations had some impact, with Max Verstappen and Kimi Antonelli also finding the barriers on the weekend.
"I may be speculating a bit because the information is only relating to Oscar. But they were uncharacteristic incidents, especially relating to Verstappen," Stella said.
"In testing we might have seen some similar circumstances.
"But we didn't have the combination of cold tyres and the kerb which was aggravated by inconsistencies in torque deployment in grip-limited phases."
Piastri's crash aside, it was also clear McLaren did not have the fastest car this year, with Mercedes and Ferrari clearly quicker to start the season.
McLaren have typically been the best at bringing upgrades in recent years, with Stella admitting it is already clear the car needs better grip and power unit output.
However, there is a concern that improving power performance may be an issue, with McLaren a customer of Mercedes and fearing that has left them at a disadvantage to the Silver Arrows.
"Even in testing we were pretty much going on track, run the car, look at the data - 'Oh that's what we have; now we react to what we have'," Stella said.
"That's not how you work in Formula One.
"What happens on track, you simulate. You know what is happening, you know what you're programming. You know how the car is going to behave.
"You also have your plans as to how you evolve it, that you have figured out before because you know what you are expecting from the car.
"Since we are a customer team, this is the first time we feel like we are on the back foot even when it comes to the ability to predict how the car will behave and how we will improve the car."
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