Oscar Piastri edged out McLaren team-mate Lando Norris to top the Sprint Shootout at the Qatar Grand Prix, as Max Verstappen remained on course to seal the world championship later on Saturday.
Piastri delivered a 1:24.454 to beat Norris by a little under a tenth of a second, in a chaotic session that saw drivers repeatedly lose lap times for failing to stay within track limits at the Losail International Circuit.
Verstappen, who appears almost certain to seal his third successive drivers' title in the Sprint - live on Sky Sports F1 at 6:30pm - was third behind the McLarens.
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Verstappen can guarantee the title with three points, but will become champion regardless of his own result if his Red Bull team-mate Sergio Perez, who qualified eighth, finishes outside the top three.
George Russell was fourth ahead of Ferrari duo Carlos Sainz and Charles Leclerc, but his Mercedes team-mate Lewis Hamilton will start from 12th after making a surprise SQ2 exit.
Nico Hulkenberg took an impressive seventh for Haas, while Aston Martin's Fernando Alonso and Alpine's Esteban Ocon rounded out the top 10.
The session began 20 minutes later than originally scheduled and with altered track limits, after the FIA made changes on "safety grounds" following tyre manufacturer Pirelli revealing concerns relating to data from Friday's practice session.
While the 19-lap Sprint later on Saturday looks set to remain unaffected, aside from the layout alteration between Turns 12 and 13, Sunday's race could see drivers forced to make three pit stops to ensure the avoidance of tyre failures.
Qatar GP Sprint Shootout Result
1) Oscar Piastri, McLaren
2) Lando Norris, McLaren
3) Max Verstappen, Red Bull
4) George Russell, Mercedes
5) Carlos Sainz, Ferrari
6) Charles Leclerc, Ferrari
7) Nico Hulkenberg, Haas
8) Sergio Perez, Red Bull
9) Fernando Alonso, Aston Martin
10) Esteban Ocon, Alpine
Chaotic start to Sprint Shootout
After a dramatic start to the day following the FIA's announcement, more chaos would follow during the Sprint Shootout.
Not for the first time during the 2023 Formula 1 season, track limits was the cause, with drivers struggling to avoid breaching them and consequently having lap times deleted.
Their task was made even more difficult on this occasion by the layout being altered, with the white line - which they must keep at least a wheel on the trackside of - brought 80 centimetres inward from the kerb in an attempt to reduce the stress being placed on the tyres.
An extra 10-minute 'Practice Familiarisation' session took place before the start of the Sprint Shootout, but it did not seem to help much when the serious action began.
In SQ1, Yuki Tsunoda was the most notable victim, as a time good enough to have sent him through was wiped out by a breach at the updated corner.
In the second segment of the session, Hamilton wasted his first flying lap by running wide at the same part of the track, and also lost his final effort, which ultimately would not have been good enough to send him through.
Piastri seals bittersweet success for McLaren
Drivers were also struggling to stay in bounds at Turn 5, and Verstappen was perhaps thrown off after losing his first flying lap in SQ3 with an infringement, and opening the door to the McLarens.
Norris had appeared the most likely candidate to challenge Verstappen throughout the weekend, but it was his rookie team-mate who denied the Dutchman a repeat of the pole position he took in Friday's qualifying.
Norris appeared on course to outpace Piastri in the closing moments, but ran wide at the final corner and had to settle for second place earned by his previous flying lap.
While a first start from the front of the grid, albeit in the shortened Sprint format, is undoubtedly a special moment for the 22-year-old Australian, Saturday's success will be somewhat bittersweet for McLaren.
Track limits breaches in Friday's qualifying mean Piastri starts sixth and Norris 10th in Sunday's race, when they clearly had the pace to at the very least challenge Verstappen for pole.
It now remains to be seen whether they can soften that blow by holding off Verstappen for victory in a Sprint that looks set to be all about the Dutchman regardless of whether or not he wins it.
Will Max Verstappen wrap up his third world championship at the first attempt at the Qatar GP? Watch every session of the Sprint weekend live on Sky Sports F1 from October 6-8. Stream F1 on Sky Sports with NOW for £21 a month for six months