Ricciardo is making a shock comeback with his old Faenza team from this weekend's Hungarian Grand Prix onwards, replacing rookie Nyck de Vries, who was moved aside after 10 races.
The Australian's F1 return came much quicker than he had anticipated after needing to take time off following a difficult two-year spell at McLaren which sapped the 34-year-old of confidence.
After Ricciardo returned to Red Bull as a third driver this winter, team boss Christian Horner commented how the team almost didn't recognise the old Ricciardo during his first simulator outing, as he had seemed to pick up all sorts of bad habits while trying to adjust his driving style to the McLaren.
When asked by Autosport how he managed to find his old form again in the simulator, Ricciardo said being reunited with his former race engineer Rennie, who now runs the Milton Keynes simulator, has helped him regain confidence.
"When I first drove the sim, obviously I haven't been in a race seat for a few months," Ricciardo said.
"I could see myself last year lacking a little bit of confidence. You just get other thoughts that creep into your mind.
"Going back into Red Bull was exciting for me, but I was also a little bit like nervous excited. Those first few runs on the sim, it took a little bit to shake a few things out and try to just find my old self again.
"I think what helped a lot was working with Simon Rennie, my engineer at Red Bull back when I was racing there, he's been running the sim. Getting a bit of familiarity working with him quickly got my confidence back."
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Ricciardo's rebuild in the simulator led to a Silverstone Pirelli test that finally convinced Red Bull that he was ready to come back and replace de Vries.
The eight-time grand prix winner believes his familiarity with the Red Bull cars' enduring DNA made getting up speed easier than with the more alien behaviour of the McLaren, which, according to his former team-mate Lando Norris, is still very hard to drive to this day.
That allowed Ricciardo to regain trust in his natural driving style, which he felt forced to move away from at Woking.
"I think the really nice thing was that once I shook off the cobwebs, although the car is different from five years ago, it still felt for me like a Red Bull car," he said.
"I felt like everything that I used to really like about the car was still existing, like the DNA, and that as well filled me with some confidence that I could start to drive really the way I like or the way I want.
"The last tick of the box was driving the real car to make sure that I could do it on track. And the test went well, and we're in a good place."
