Nico Rosberg has shown huge adulation for old rival Lewis Hamilton after he won his sixth World Drivers' Championship in Austin last night.Rosberg, who pipped Hamilton to the title by five points in 2016, was watching the drama unfold yesterday and took to Twitter to show his praise for Hamilton.Rosberg tweeted: "Karting together who would have thought that we'd both be #F1 world champion one day. And you? You’ve achieved it for the sixth time – on your way to becoming the GOAT. Impressive! My greatest respect – enjoy these moments and celebrate. Well deserved, @LewisHamilton 👍 #USGP."Rosberg, who now works for Sky Sports F1, can lay claim to being the only driver to finish a season ahead of Hamilton in the hybrid era, after rules changes by the FIA came into place in 2014.When discussing Hamilton's sixth title, he added: "He is absolutely incredible, we raced each other when we were 13 and 14 years old - we were best friends, we used to go on holiday together and dream big, one day in Formula 1 fighting for championships."

Hamilton's remarkable tally of 83 race wins is just eight behind Schumacher's all-time record of 91, and Rosberg believes that Hamilton will soon be Formula One's greatest driver.

"He's now closing in on becoming the greatest of all-time, and who would have thought that was even possible, for someone to even reach Michael Schumacher."

Despite an intense rivalry on the track, an incredible amount of respect has been shown to Hamilton by Rosberg, who knows better than anybody how hard it is to win one Drivers' Championship, let alone six.

Although the German sometimes still aims jibes at Hamilton, it's clear that his admiration for him and respect for him is as strong as ever.