As Daniel Ricciardo announces a switch to Renault for 2019, Laurence Edmondson wonders who might take his Red Bull spot. (2:06)

Daniel Ricciardo says his switch from Red Bull to Renault for the 2019 Formula One season is one of the toughest decisions he has made in his entire life.

Ricciardo's surprise switch to Renault shocked the F1 world when it was announced yesterday afternoon. It was widely expected that the Australian would remain alongside Max Verstappen for next season, where Red Bull will run Honda power units for the first time.

In a video posted on his personal Twitter account, Ricciardo said: "The news is out, it's real. By far the toughest decision I've made in my racing career but 29 years living on this Earth, it was actually one of the toughest life decisions I've made.

Daniel Ricciardo sits fifth in the drivers' championship, 13 points clear of Red Bull teammate Max Verstappen. Mark Thompson/Getty Images

"Sad to move on, absolutely. Excited for the challenge at Renault. It's been a ten year journey with Red Bull. I was on the junior programme in 2008 and some amazing memories from there. Things I will always be grateful for and I will never forget that ride.

"Personally I felt it was a time where it was good to move on and have a fresh start somewhere else. I think it will be healthy for me so excited for what lies ahead for me at Renault. Just want to thank Red Bull Racing, Red Bull the company, for everything they've done for me, I really appreciate it. We've got nine races left to kick some ass, so let's get it.''

Ricciardo leaves Red Bull having spent the past five seasons with the team, winning on seven occasions and claiming 29 podium finishes.