Piastri was running second behind race leader Max Verstappen in the early stages at the Hungaroring when at the first stops, the team elected to pit third-placed Norris instead.
The extra pace that Norris got from fresh rubber was enough to help him leapfrog Piastri, who stopped one lap later, and found himself emerging from the pits behind his team-mate.
While the decision to pit the second car was slightly unusual, because teams normally give the better option to their lead car, McLaren team principal Andrea Stella has explained the reasoning behind its decision.
He said the team chose to stop Norris first because there was a risk of him getting undercut by Lewis Hamilton behind him, so it was better to stop the Briton first.
It also was not anticipating that his pace on fresh rubber would be enough to overhaul Piastri, who had looked solid in the first stint.
“In terms of the undercut that we had at the first stop, you just go really with the sequence that is natural, because you cover with the car that is more at risk, and then you cover with the other car,” explained Stella.
Source: Autosport