Ferrari's Charles Leclerc set the pace on the final Friday of F1 2023 but the second practice session in Abu Dhabi was heavily disrupted by crashes for Carlos Sainz and Nico Hulkenberg.
Two separate red-flag periods meant drivers only got half of the hour-long session on track, significantly condensing teams' run plans, and ensured there were few absolute conclusions to be drawn from the opening day's action at Yas Marina Circuit.
Ferrari's Leclerc posted the quickest time in the laps that were completed with a best lap of 1:24.809, 0.043s clear of McLaren's Lando Norris and 0.173s of Red Bull world champion Max Verstappen.
Sainz's session in the other Ferrari had lasted just eight minutes when he flew off the track at high-speed at Turn Three.
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With his car unsettled by a bump on the 170mph entry to the corner that had already caused problems for other drivers, Sainz lost the back end and the car and spun off off track into a big impact with the tyre barrier.
Sainz said he was okay and climbed out of the heavily-damaged car, while the session was red-flagged for 22 minutes - nearly a quarter of the scheduled running - while marshals completed repairs to the damaged barriers.
"It was a pretty big crash but in the end with these safe cars you can get away with these pretty big hits pretty untouched, and that's the car. I'm a little bit sore but nothing to worry about," said Sainz after the session.
"For some reason there has been a change in the track compared to other years. There are two bumps, one at the exit of Turn Two and one at the entry of Turn Three, with this generation of cars it is upsetting the cars a lot.
"It nearly caught me out in FP1, I changed a few things in the set-up and in the line trying to get ride o fit, but for some reason again in that lap it surprised me. It must have been an angle or the way I took the bump and it made me a passenger from then on."
No sooner had the track gone green after the repair barriers than cars had to come back into the pit lane again for a second red flag when Nico Hulkenberg spun his Haas and hit the inside barriers coming out of Turn One.
A further seven-minute delay ensued before the session resumed again, with drivers at least this time able to run without further delay to the flag.
But the data gathered by teams - particularly on high-fuel long race-style runs - is nowhere near what it would usually be on a Friday.
"It puts everyone in a situation where they don't really know what they are going into on Sunday," said Sky Sports F1's Naomi Schiff.
"This was the most representative session and they weren't able to get their long runs done, which is going to be what matters for them on Sunday."
Underlining the uncertainty at the end of the first day, Alfa Romeo's Valtteri Bottas finished up in fourth on the timesheet ahead of Red Bull's Sergio Perez and Mercedes' George Russell.
Lewis Hamilton was eighth quickest, finishing between the second Alfa Romeo of Zhou Guanyu and Alpine's Pierre Gasly.
Earlier, and as drivers attempted to make up for lost time and get back onto the track, Verstappen complained over team radio that he had been blocked in the pit lane by Mercedes duo Hamilton and Russell. He took matters into his own hands by overtaking the pair in the narrow pit lane exit before the tunnel.
"They have to move!" said Verstappen after the session. "They are all driving slow and I want to go out because we are all limited on time and they keep on driving in the middle. Then I went to pass, they try to squeeze me in the wall. So a bit silly."
McLaren show early promise on an unusual F1 Friday
Friday's practice running in Abu Dhabi is always something of a compromise for teams at the best of times given the opening session takes place in particularly warm day-time conditions that are not are representative of the slightly-cooler weather of the evening when qualifying and the race happen under floodlights.
Added to that was that this year in Practice One, nine of the 10 teams handed at least one of their cars over to a rookie driver in order to complete their requirements for young-driver running in Friday sessions this year.
And although all the usual race drivers were back in their respective cockpits for the later session, the red flag delays that ate up nearly half the session meant they could not complete their usual long-running which is crucial for planning for Sunday's race.
However, some clues as to the potential pecking order still emerged - including confidence from McLaren's drivers that they are in strong shape following a difficult outing in Las Vegas last week.
"It was decent, messy of course, not many laps today," said McLaren's Norris, who finished a close second to Leclerc.
"I got comfortable and confident very quickly, which is always important on a day where you miss FP1.
"For just one session today, I was happy. The car was obviously quite quick. Definitely a bit to find.
"I think it's going to very close here in qualifying tomorrow, so one or two tenths is easily five-six positions come [Saturday]."
Team-mate Oscar Piastri, who was 10th quickest, added: "Maybe we didn't fully see what Red Bull's pace was like today, but I think we're fighting well and truly at the front."
Verstappen, aiming to end his dominant season with a record-extending 19th win, said Red Bull had work to do to get the RB19's handling under control.
"The balance was very off - a lot of understeer, a lot of jumping, so definitely a few things to figure out," he said. "I also didn't expect to be so far off, so that's also a bit of a question mark for us."
Sky Sports F1's live Abu Dhabi GP schedule
Saturday November 25
- 10.15am: Abu Dhabi GP Practice Three (session starts at 10.30am)
- 12.15pm: F2 Sprint
- 1.15pm: Abu Dhabi GP Qualifying build-up
- 2pm: Abu Dhabi GP Qualifying
- 4pm: Ted's Qualifying Notebook
Sunday November 26
- 9.10am: F2 Feature Race
- 11.30pm: Grand Prix Sunday Abu Dhabi GP build-up
- 1pm: The ABU DHABI GRAND PRIX
- 3pm: Chequered Flag: Abu Dhabi GP reaction
- 4pm: Ted's Notebook
After the thrills of Las Vegas, Formula 1 heads to Abu Dhabi's Yas Marina Circuit for the 2023 season finale and another stunning spectacle under the lights. Watch the Abu Dhabi weekend live on Sky Sports F1, with lights out on Sunday at 1pm. Stream F1 on Sky Sports with NOW