Australia's hope found frustrations at the Yas Marina circuit on Friday, forced to take a mandatory break in morning practice before taking time to find his feet in the under-lights second session when he ended 11th quickest, 0.68sec slower than Norris's best lap of 1min 23.083sec.
It was the perfect boost for the Briton, who's 12 points ahead of Max Verstappen and 16 ahead of McLaren colleague Piastri, as the Dutch champion, second quickest on the day, still finished 0.363 slower than Norris in his Red Bull under the floodlights.
Verstappen was also noted by stewards for impeding Norris in the first flashpoint of the weekend after the champion had been fed wrong information by his race engineer, but they decided not to investigate further.
"What's this guy doing? I almost crashed," Norris had been left exclaiming.
For Piastri, desperate for the pace he had in Qatar last weekend when only McLaren's strategy blunder stopped him sweeping every session, it felt a stop-start day as, first, he spent the morning on the team's pitwall.
While Norris led Verstappen by 0.008sec in another one-two, he gave up his seat to reserve Pato O'Ward in a session designed largely for young prospects and development drivers.
Piastri was doubtless itching to get out on track as his McLaren boss Zak Brown joked: "There's some guy that has taken my seat!"
Not much of a laughing matter for Piastri, though, as he started on the back foot in the second session, more representative of what they'll all face on Sunday.
He locked up on his quickest lap and couldn't get near Norris's fastest, with Brown noting: "Oscar is not totally dialled in yet but he will get there."
Piastri certainly didn't seem concerned, appearing his usual unflappable self as he told reporters: "Finding my feet. Clearly, some things to try and improve for tomorrow, but after just one session, not too bad.
"It's more just little details, the car feels like it's in a pretty decent place, but just didn't get the grip out of it on that first soft lap. So some small tweaks for tomorrow, of course. It didn't feel perfect out there, but nothing major."
Norris didn't evidently want to get too high himself so early in the week, saying: "Obviously, from the times, things look good at the minute, but I still want a bit more from the car. I'm not completely happy, or completely confident.
"We all know it gets a lot closer going into quali. So nothing to smile about just yet."
Verstappen had more than a few grumbles about the Friday set-up of his Red Bull, complaining in the morning that "something is broken on the car".
Asked what the main areas of issue were by his race engineer Gianpiero Lambiase, he replied: "It is everywhere now."
Mercedes' George Russell, who could play a key role yet in Sunday's race, was third quickest in second practice.
Brown, meanwhile, revealed McLaren might yet employ team orders in the race, after speculation all week that Piastri could be asked to move over for Norris, sacrificing his own slight championship chance if it appeared Verstappen could be heading for overall victory.
Brown admitted: "If, as the race develops, it becomes clear one of our drivers 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."
He 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."
