Lewis Hamilton came within inches of being rear-ended by Haas driver Nikita Mazepin as the dangers of the Jeddah Corniche Circuit were again brought sharply into focus.
Immediately after crossing the line to start a cool-down lap, the seven-time champion first forced AlphaTauri's Pierre Gasly to take to the turn one run-off area as he closed in behind.
But worse was to follow as the Mercedes driver then reached the first of the twisty parts of the 27-turn, 6.1km circuit self-proclaimed as the 'fastest street track in F1'.
Trundling through turn eight, Haas driver Nikita Mazepin was forced to cut the corner, scything his way through with Hamilton to his left and a wall to his right.
Asked by Haas as to his thoughts on the incident, FIA race director Michael Masi said: "Not great at all. I will deal with it directly with the team. I've also had a chat to them here because no flags of any form were shown through that sector."
Ahead of qualifying, Masi warned drivers not to create a gap through turns 23-25, however, it appears such a warning should be extended to other areas given the closing speeds of cars through blind corners.
After finishing quickest in both sessions in Friday practice, Hamilton was forced to settle for second best behind Red Bull's Max Verstappen who found pace on the soft-compound tyre compared to his F1 title rival, setting a leading time of one minute 28.100s, finishing two-tenths clear.
It is understood Mercedes changed Hamilton's engine overnight, switching from an older system used in Friday practice to the one that propelled him to a remarkable victory in the Brazilian Grand Prix when it was used for the first time.
The conditions, with the sun setting over the Red Sea and not the night-time run that will be experienced in qualifying and the race, were not far shy of optimal, especially with plenty of rubber laid down from the F2 race beforehand.
Hamilton led the way initially with a time of 1:29.605s on the hard tyre before being usurped by Red Bull's Sergio Perez by a tenth of a second, albeit on the soft rubber.
The Mexican's time at the top, however, was very short-lived as within seconds the seven-time F1 champion reclaimed the quickest time with a 1:29.197s.
Hamilton continued on the white-striped tyre and for the first time across practice he became the first driver to dip into the one minute 28s, and significantly so with a lap of 1:28.314s to lead by nine-tenths of a second, but that proved to be his best lap.
Verstappen moved to within a third-of-a-second soon after, but on the soft tyre before going quickest by a tenth of a second at the halfway point of the session.
Hamilton's first attempt on the soft rubber was woefully shy of his time on the hards, to such an extent he backed off in the final sector, and after pitting to take on a fresh set of softs, Hamilton then finished 0.460s behind his title rival.
It was at that point Hamilton encountered his double dose of trouble, first with Gasly and then Mazepin.
Both Verstappen and Hamilton marginally improved in the closing stages, with the former setting his 1:28.100s, with Hamilton 0.214s down.
Perez finished third quickest but just over half-a-second back followed closely by the AlphaTauri's of Yuki Tsunoda and Gasly, with Valtteri Bottas a lowly sixth given the issues on the soft tyre for Mercedes.
The Finn was the only other driver to finish within a second of Verstappen as seventh-quickest Charles Leclerc was 1.001s adrift in his Ferrari, with team-mate Carlos Sainz 0.048s in eighth.
Alpine's Esteban Ocon and Lando Norris in his McLaren completed the top 10, with the latter's team-mate in Daniel Ricciardo down in 14th, 1.589s down.
For the third successive session, Mazepin was slowest, 2.879s back.