Ricciardo managed to find a set-up breakthrough after his first regular grand prix weekend back from his five-race injury lay-off and put the AlphaTauri fourth on the grid for the Mexico City event.
He backed that up by running in the top five for the first half of the race, with an unfortunately timed red flag leading to him dropping back to seventh at the finish.
The AlphaTauri's competitiveness, which Yuki Tsunoda also displayed before clashing with McLaren's Oscar Piastri, warrants a word of caution as it is thought to be largely circuit-specific.
The Faenza squad could deploy its excellent mechanical grip at the high-altitude Autodromo Hermanos Rodriguez while being punished less for its draggy car.
Nevertheless, Ricciardo showed a first glimpse of the kind of form and confidence reminiscent of his Red Bull days, something which didn't go unnoticed by the team.
"It's great to see Daniel performing so well and it fully endorses the reason why we brought him back into AlphaTauri just prior to the summer break," said Red Bull team principal Horner.
"I thought he was outstanding this weekend fighting a Mercedes in an AlphaTauri. Had it not been for the red flag, he would have probably finished further up.
"A great performance from him and certainly, it looked like the Daniel of old."
Horner brushed off suggestions that Ricciardo was still limited by the type of F1 car he can excel in, saying his curtailed McLaren stint was a mental battle more than anything else.
"That's a bit of a fallacy to say," he said. "I think that this sport is as much in the head as it is anywhere else and I think he's back to his old self.
"You can see he's relaxed, he's confident and he came into the weekend fully motivated after a tricky Austin.
"Look at the delta to Max [Verstappen] as well. It was less than a tenth to Max. A remarkable performance by him."
Ricciardo's breakthrough result for AlphaTauri came in a race where Red Bull's Sergio Perez, who occupies the seat Ricciardo is chasing, took himself out in an ambitious three-wide overtake in the first corner.
But Horner, who publicly defended Perez's actions, batted away any connection between the two very contrasting race outcomes, even if his commitment to Perez was phrased less watertight than earlier comments he made about the Mexican's future.
"Checo has an agreement with us for next year and that's our intention, for him to be in the car in 2024," Horner carefully stated.
"We'll give him all the support we can to ensure that he finishes second [in the drivers' standings] but there's no prerequisite that if he doesn't finish second, you're out."
