The New Zealander has been drafted into AlphaTauri after Daniel Ricciardo broke a bone in his hand when he went off in FP2 avoiding the crashed car of Oscar Piastri.
Ricciardo went to a local hospital and word soon came back to the Red Bull camp that he wouldn't be able to drive for the rest of the weekend.
Current Super Formula frontrunner Lawson knows Zandvoort well having contested the F2 event last year, and he is also familiar with the AlphaTauri team and its engineers.
He did the Abu Dhabi rookie test at the end of 2021 with the Faenza outfit and undertook two FP1 sessions in 2022, in Belgium and Mexico.
He then gained further F1 track mileage with Red Bull in FP1 in Abu Dhabi, prior to doing the rookie test at the same venue with the senior team.
Horner admits that the 21-year-old faces a tough challenge given the limited running he will have this weekend, but is confident that he will cope.
"That's why he's here," he said when asked by Sky F1 about Lawson's mindset ahead of his debut. "He's the reserve driver for both teams, for exactly a scenario like this.
"So it's in at the deep end, one practice session, in a car I don't think he's driven before, and then qualifying - at one of the toughest tracks.
"That's F1, you get your chances, one person's misfortune is another's fortune. But I'm sure he'll be fine."
Horner confirmed that there was no possibility of Ricciardo returning to the cockpit this weekend.
"Oh no, he's broken a bone in his hand," he said. "A great shame for him, because the session was going well for him, and just unlucky. Oscar, by the time he saw him, it was very late.
"And the whip back from the steering wheel is what's done the damage. A shame for him, but good to see that he's okay. And he's still in good spirits."
Ricciardo is expected to be treated by Doctor Xavier Mir, who is well known for working with MotoGP riders, and also played a key role in Lance Stroll's quick recovery from a cycling accident earlier this year.
"I think you've just got to take it one day at a time," Horner noted. "He's got a good medical team that he'll be working with. These guys recover incredibly quickly.
"We saw Lance earlier in the year with I think what was a multiple break [rather] than what Daniel has. He's a tough Aussie. I'm sure he'll be eager to get back in the car as quickly as he can."
