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.
Source: Autosport