On a Friday intensified by a need for data on Formula 1's first visit to Portimao, exaggerated by a 30-minute tyre test at the beginning of FP2, Stroll's session was curtailed after contact with the Red Bull at turn one.
Verstappen pulled alongside the rear-wheel of the Candian's car before the Racing Point swept across the apex, caused by what seemed to be a misunderstanding from both drivers as to the other's run-plan.
Verstappen was able to return to the pits as the red flag came out, whereas Stroll was left stranded in the gravel, leaving Szafnauer damning in his verdict of the Dutchman's driving.
"It looks like Max didn't realise we were doing two quick laps there," he told Sky Sports F1. "He shouldn't have been where he was.
"We often do it, other teams do two, so it's pretty common. You don't always do push-cool-push-cool-push, sometimes you do push twice just to see what the tyres are like.
"Had he known he was there he wouldn't have turned in. We didn't anticipate Max to go there, I mean what was the purpose?
"It's just ridiculous. For what gain? I can assure you 100% Max knew Lance was there. There's no way he doesn't know Lance was there, but Lance doesn't know Max is there. It's pretty simple to me."
Verstappen's team boss Christian Horner took a more diplomatic stance, exonerating his driver of complete blame and opting to suggest both were at fault for the collision.
Also speaking to Sky Sports F1, Horner confirmed Szafnauer's belief that Verstappen had expected Stroll to back off following the completion of his lap.
"The way I see that, you have to go back to the previous lap," he said.
"Lance is going into the last corner. Max has let him go because he wants to take a tow. He is assuming that Lance is obviously finishing a lap, he is not aware he is taking a second lap.
"He has let him past, tucked up behind him as he did with [Valtteri] Bottas in Sochi, taken the advantage of the tow assuming that he is going to back out and he knows he is there and is up the inside.
"He felt Lance was later on the DRS and then obviously Lance, for whatever reason, hasn't seen him and he has committed to the corner and turned in.
"So I think one was expecting the other to back off, or maybe both of them were expecting the other to back off. If that were a race, Max would have been deemed to have been up the inside and therefore the car on the outside should have given way."
Horner, however, questioned as to why Stroll was holding rank considering his compromised final corner, again suggesting both drivers had to take a portion of the blame.
"The point that [Max] has gotten there, it is too late to get out of it," added Horner. "You could argue that Lance has screwed up his entry onto the lap, why is he driving down the straight with the DRS wide open?
"If I am absolutely honest, you can say both have a role to play. Max has gone for the tow, he is assuming he is going to back out. He doesn't know Lance is going for a second lap. We saw that Lance was looking at his dash and maybe didn't even know he was there."
Both drivers have been summoned to the stewards who will determine who was at fault, if anyone.
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