The Australian Formula One star's decision to sign with Renault on a two-year from 2019 stunned the motorsport world when it was confirmed he was exiting Red Bull on Friday.
Sainz could slot in at Red Bull but the previous pairing of him and Verstappen at Toro Rosso was far from smooth and the Dutch 20-year-old is now the senior team's clear focus.
"It was probably one of the most hard decisions to take in my career so far", Ricciardo Renault's statement confirming his deal.
Carlos Sainz, who Ricciardo will replace at Renault, is likely to join McLaren although the Spaniard also remains in the frame to return to parent team Red Bull as Verstappen's partner.
Both Red Bull and Renault use the same engine with the former exploiting it significantly better than Ricciardo's new side which poses more questions as to why he made the move.
Ricciardo, who has won the Chinese and Monaco Grand Prix races in the current season, has signed a 2 year contract with Renault, and will partner Nico Hulkenburg. The very auto that Sebastian Vettel secured his second driver's title in, the Red Bull RB7 was also one of the most dominant Formula One cars ever made, having accumulated 18 pole positions and winning 12 of the 19 races that made up the 2011 Formula One World Championship.More news: Trump says his son sought information on Clinton from Russians in 2016
Renault are now fourth in the Constructors' Championship and are yet to win a race since returning to the sport as a fully-fledged team three years ago when they bought Lotus. Renault finished ninth in 2016 with Jolyon Palmer and Kevin Magnussen in the paddock but upped their game in 2017 with Nico Hulkenberg scoring the majority of the team's points as they finished sixth.
"It has been a 10-year journey with Red Bull".
Red Bull meanwhile need to find a replacement for Ricciardo.
An awesome journey needs an equally impressive vehicle to complement it, and they don't come much more unbelievable than the Red Bull RB7.
"Excited for what lies ahead with Renault", Ricciardo continued, "but [I] just want to thank Red Bull Racing, Red Bull the company, for everything they've done for me".
Ricciardo leaves Red Bull having spent the past five seasons with the team, winning on seven occasions and claiming 29 podium finishes.