Nico Rosberg labelled his former rival Lewis Hamilton's achievements as "completely insane" as he closes in on a sixth world drivers' championship.
Hamilton must simply finish eighth or higher in the United States Grand Prix in order to move onto outright second on the all-time lit of F1 titles, between Juan Manuel Fangio (5) and record-holder Michael Schumacher (7).
Provided 2019 doesn't provide an almighty shock, Rosberg will remain the only driver to beat Hamilton over the course of a season in the V6 Hybrid era, having secured title glory in 2016 and promptly retiring after an acrimonious intra-team battle at Mercedes.
Rosberg and Hamilton were childhood friends and rivals on the track, leaving the retired German to reflect on the magnitude of his former team-mate's achievements in his latest YouTube vlog.
He said: "We were go karting together, we were 13, 14 years old and best friends, going on holidays and saying, 'Hey imagine if one day we're going to be racing for the best team and imagine if we're fighting for the world championship'.
"But [it was] totally unrealistic [then], and now the guy is going on for a six-time world champion. It's just completely mad.
"And [he is] nearing the greatest of all time in terms of results, which is Michael Schumacher.
"It's completely insane, but of course he is just an unbelievable driver, so he totally deserves it and [he is] very, very impressive."
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