The Ferrari Driver Academy member, who currently lies sixth in the FIA F2 standings, is the latest in a line of Maranello proteges to get track time with Haas.
The team has been burned in FP1 before, with Antonio Giovinazzi crashing heavily as a rookie in Hungary in 2017, and again last year as a veteran at COTA.
With the cost cap biting and the US-owned team running its new package, an off for Bearman in FP1 would be a major setback for the team, but Steiner has faith in the 18-year-old newcomer.
"You're always a bit nervous,” Steiner said when asked by Motorsport.com about Bearman’s outing. “But, and hopefully I'm proven right tomorrow, he knows that the biggest mistake he can do is overdoing it.
“I explained to him you're always judged by the things you do badly, not the things that are good. Because if you do everything right, nobody will remember.
"But if you crash the car on your first outing in an F1 car in FP1, that will be on your resume for the rest of your life.
“If you ever make it into F1 because of that. You know how this business works, and I made him aware of that. I think he's smart enough to know that he doesn't go through anything stupid.”
Asked what was expected of Bearman, he said: "To learn as much as he can, not make any mistakes. And I think at the moment, there's not too much pressure on him doing this. I think he's in a good place.”
Bearman, who recently got his F1 baptism driving a Ferrari SF21 at Fiorano, says the message has got through.
“Of course, like Guenther said, there's no positives, nothing to win on Friday,” he said. “It's a mandatory session, and I just need to bring the car back.
“But at the same time, I'm really excited to get going, it's going to be really fun. I've already driven F1 in Fiorano. So I've got a taste of what it's like at full gas.
"This will just be building into it, and hopefully bringing some useful data for the team as well."
Asked about Ferrari’s targets for his outing, he said: "No targets from anyone, even from myself. I think it would be silly to set any expectations. My first target is just to enjoy it, really.
“Like we said, I've had it drummed into me a lot now. There's nothing to win from here. Just do a solid job, build up step-by-step, and enjoy it as well. So that's my goal."
Bearman noted that the Fiorano outing provided useful experience, albeit as the only car on track.
"The switches are something that at least I get used to with the sim and with the test in Fiorano, it's quite similar set-up to what Ferrari have, so that's nice,” he said. “Now there's other cars on track, which could complicate things a bit.
“I think for me the most complicated part is going to be the track evolution. It starts very dusty here, and with the altitude as well the grip level is low.
"I think just getting to grips with that and understanding what the car needs will be the main difficulty."
Asked about making into F1 having only turned 18 in May, he added: "It's really cool to be here so young, just have my foot in the door.
“And I think the main goal of this weekend is to get to know people and show them what I can do and come across as a good guy. And yeah, it helps that I'm young, I've got a lot of time to get here."
