While McLaren teammate and overall leader Lando Norris lapped quickest, just 0.008sec faster than his nearest contender Max Verstappen, Piastri had to give up his seat on Friday morning to reserve Pato O'Ward in a session handed over largely to young prospects and development drivers.
Sitting instead among the McLaren pitwall, Piastri was doubtless itching to get out on track as his McLaren boss Zak Brown was left joking: "There's some guy that has taken my seat!"
It probably wasn't much of a laughing matter for Piastri, though, especially if he had heard Brown also reveal that McLaren might yet employ team orders to manage the F1 title fight if one of their drivers had a "significantly better chance" to win in Sunday's race.
With Norris 16 points ahead of his Australian teammate -- he's also 12 points clear of Red Bull's champion Verstappen -- it is, of course, more likely that any team orders will mean Piastri taking the hit.
It's prompted speculation that Piastri could be asked to move over for Norris, sacrificing his own slight championship chance, if it appears that Verstappen could be heading for overall victory -- but both drivers had reported on Thursday that the scenario hadn't been discussed.
But Brown said on Friday: "In the sense of team orders, as long as both drivers have a chance to win the world championship, which they clearly do sitting here right now, then it's business as usual. They're free to race. Obviously, we'll be practical and realistic.
"If, as the race develops, it becomes clear that one has a significantly better chance than the other, then we're a team that wants to win the drivers' championship and we will race accordingly, to do whatever we can to get that driver in front to try and win the race."
Brown didn't say what sort of chance would qualify as "significantly better," but indicated team orders would only come into play if "it becomes clear that both (Norris and Piastri) can't" win.
Asked if he believed Piastri would agree to any order to help out Norris, Brown said: "Yes. Our drivers have always complied with team wishes, just as we comply with their wishes.
"I've got no doubt either of our drivers will continue to race as they've done brilliantly, in the best interest of the team."
Norris and Verstappen were only two of 11 regulars taking part in the session, with the Dutch champion having sounded worried about his car's handling on a slippery surface in the unrepresentative afternoon heat.
"There might be something broken on the car," he reported.
But Friday's afternoon session, in which Piastri will get his first chance, will be the important practice under the floodlights which will be more representative of race conditions.
