Piastri made contact with Yuki Tsunoda twice during a fraught battle in the second part of the race.
On the second clash the AlphaTauri driver was pitched off the road when he tried to pass on the outside at Turn 1. The FIA investigated the incident, but ultimately took no further action.
A few laps later Piastri was asked to let Norris by so that the British driver could attack the cars ahead in the course of his spectacular drive from 17th to fifth.
Piastri meanwhile had to settle for eighth, crossing the line some 10 seconds behind Norris.
"Yeah, some big moves," he said when asked about the Tsunoda fight. "I think hard racing.
"The one in the end, I'm not really sure what happened for me, I was just braking and then we touched wheels. So nothing really more than that.
"I had some damage at that point. Lando was very quick compared to everyone, I think. So it didn't make any sense to try and battle each other.
"In the end, it meant Lando got another two spots. So yeah, it worked out well for the team."
Asked if the damage was the sole cause of the pace deficit to his team-mate Piastri said: "I think still an element of tyre management, definitely.
"Of course, the damage didn't help, and of course I was battling pretty hard with Yuki, which wasn't helping either. But still something to try and improve."
Piastri admitted that following recent results an eighth place was underwhelming.
"I think with the pace we have in our car now, I don't really think that it’s much to brag about," he said. "Still always looking for more.
"Just struggled a bit in certain parts. And made life much, much more difficult, I think.
"The pace with the cars around was similar. Lando was just very, very strong in the last stint, and was able to come through."
McLaren team boss Andrea Stella confirmed that tyres as well as the car damage played a part in Piastri’s afternoon.
"On Oscar's side with the contact, we lost between 20 and 15 points of downforce," said the Italian. "Which in a track like this, is three or four tenths, so that was a bit of a shame.
"At the same time, Oscar's tyres were more used than Lando's. It's similar to what we saw in Austin, in the sprint.
"Oscar had more damaged tyres, and it looks like it makes quite a bit of difference. And then you start to get under pressure.
"Then you need to manage, you need to use your battery to defend, and you enter in a loop in which you struggle to find the pace."
Additional reporting by Filip Cleeren
