The Kiwi stepped into the car on Saturday and gained his initial experience in wet conditions, qualifying 20th and last, after Ricciardo was ruled out with a broken hand in an FP2 crash.
He sampled the car in the dry for the first time in the laps on the way to the grid and after the start he joined the first lap rush for intermediates.
As one of the early stoppers he briefly held fastest lap on the third lap of the race, and he ran for a while in 11th place.
PLUS: How Lawson stayed afloat in his sudden F1 debut
However, he received a 10-second penalty as AlphaTauri had blocked Kevin Magnussen’s exit from the pits by double stacking Lawson behind team-mate Yuki Tsunoda, the delay dropping him back at his next stop.
After an eventful afternoon that at one point saw Lawson pass the ailing Ferrari of Charles Leclerc, he was eventually classified 13th of the 17 cars running at the flag.
“I mean, the poor guy getting dropped in a car he's never driven, wet, dry conditions, everything being thrown at him, I actually think he did pretty well,” says Red Bull team principal Horner.
“And he actually overtook Max [Verstappen] on Max's out lap as he changed onto the intermediate tyres at the end there.
“To finish a race like that in itself with the lack of experience that he has, I thought in very difficult circumstances he applied himself very well.”
AlphaTauri team principal Franz Tost stressed that it was too early to draw any conclusions about his long-term prospects.
"He did a good job because it was really difficult,” the Austrian told Autosport.
“He had to go out in the wet conditions, and there were not so many laps in the dry. And he didn't make any mistakes. A very good job.
"He must wait a little bit. To come into F1 is one story, how the driver then develops and increases his performance is another story. You have to wait.”
Lawson himself admitted that the afternoon was about gaining experience in the mixed conditions.
“It was a little bit sketchy,” said the 21-year-old. “Conditions were all over the place. Rolling up to the grid it started raining, definitely wasn't the best feeling. But throughout the race I was obviously learning a huge amount.
“The first part wasn't the best. We lost a lot of time with the stacking in the pitstop, and then the penalty. So that's all part of it, obviously.
“But the second half I think I started to get a bit of feeling on the softs in clean air, and then on the inters as well. I felt a lot more comfortable than yesterday [Saturday].
“You always look back, and I'll reflect on this. And there's definitely things I would have liked to do better, but I think I'm reasonably satisfied with that.”
Regarding his brief tussle with Leclerc, he said: “Yeah, that was quite eventful, to be fair. I think he was struggling a lot on the softs. At the time I passed him, he just passed me back down the straight.
“So it was a little bit frustrating, but obviously, it's good to get experience. I feel like I had experience of every situation in that race with multiple pitstops, wheel-to-wheel racing, rain, dry. So it was a good learning experience.”
Lawson will continue to deputise for Ricciardo at this weekend's Italian GP and until further notice while the Australian recovers from surgery on his hand.
