While on a hot lap through the Jeddah Corniche Circuit's snaking high-speed blasts, Sargeant had to take evading action to avoid a slow-driving Lewis Hamilton through Turn 10.
As Hamilton moved over to the racing line, Sargeant had to jink right to cross the kerbs, labelling the near-miss as "dangerous" on the team radio.
After the session Hamilton and Sargeant were both called to the stewards, who handed out a warning to Hamilton and a €15,000 fine to Mercedes for what they deemed a "serious failure" to keep its driver informed of oncoming traffic.
"The Stewards heard from the driver of Car 44 (Lewis Hamilton), the driver of Car 2 (Logan Sargeant), team representatives and reviewed positioning/marshalling system data, video, team radio and in-car video evidence and determine that Car 44 impeded Car 2 at Turn 11," the stewards' verdict read.
"As a result, Car 2 had to take evasive action by going off the track to avoid a collision. Had that not been done, there would have been a serious, high-speed crash.
"Having listened to the team radio, it was clear to us that the team of Car 44 failed to warn their driver of the fact that Car 2 was arriving on a fast lap.
"That was a serious failure on the part of the team, particularly given the speeds on this circuit and the nature of turn 11, which is at the end of a series of high-speed corners where driver visibility is impaired. We therefore issue a warning to the driver and impose a fine of €15,000 to the team."
"Difficult day; just lacking confidence in the rear of the car," Hamilton reflected after setting the eighth-fastest time, over six tenths behind Aston Martin's pacesetter Fernando Alonso.
"On the set-up we did some work session to session, changed the car quite a bit but the underlying issue with the rear end that I'm struggling with, so I had a couple of really big moments out there.
"In these high-speed areas you've got to have full faith in the car and I just don't have that yet."
When asked for his expectations for qualifying, given team-mate George Russell set the second-fastest time on Thursday, Hamilton said: "I don't know, we're going to have to go through the data, but George is obviously a lot happier with his car.
"We kind of went in different directions today, we're all trying different things to try and find the right solution for the car. All I want is a stable rear and then I'll be happy, so that's what I'm working on."
