Was yesterday one of the most important days in the history of GP racing? It's hard to believe that it wasn't. In case you were in a cave somewhere for the past 24 hours, Italian Valentino Rossi won the South African GP, the opening round of the 2004 MotoGP season.

In the end, Rossi's South African accomplishment proved his detractors wrong, and may have proved to the world that he is indeed the greatest rider of the modern era and may be the best rider of all time. The story lines beneath his epic win underlines his accomplishment. He became the first-ever rider since Sheene to win four opening GPs in a row, the first rider ever to win the last race of one season and the first race of the next season on two different makes of motorcycle, and in doing so handing Yamaha their first GP win since 2002.

Honestly, he is an unlikely hero. To see Rossi in the flesh is confounding, because his appearance flies in the face of everything we've been taught about what sort of physical specimen is required to race a 200+ horsepower motorcycle. Mat Mladin, Aaron Yates and Kenny Roberts Junior are broad-shouldered men with forearms and thighs like those you would find on a boxer. Conversely, Rossi is a willowy little man; so slight that one of the three riders mentioned previously could pick him up and throw him. When I last saw him, Rossi was wearing a watch on his petite wrist, cinched tight. And it still hung loose. He looks like Kevin Schwantz did when he raced a 500, honestly: porcelain-like.

Although svelte, Rossi embodies the bedrock of what it takes to be a motorcycle racer. You've got to be brave, talented and fast. Physical conditioning is not nearly as important as mental conditioning, obviously. Is Rossi in decent physical shape? Of course. Is he at the top of the fitness scales for his height and weight? Clearly not. Does he dwarf the GP grid in terms of mental strength and talent? Yes.

Rossi's gamble, to defect from Honda and join arch-rival Yamaha was high-stakes. Many before him have flirted with it (Schwantz to Yamaha, Doohan to Yamaha, etc) but no one besides Eddie Lawson has actually has made the controversial switch, and in Lawson's case he was presuming that when he left Yamaha for Honda in 1989 that the Honda was a better GP bike—it wasn't until he actually rode it that he discovered the NSR500 was an evil handling pig. In general terms, Rossi's move is unprecedented. Riders don't leave Honda; they aspire to Honda, something Yamaha's long-suffering race manager Lin Jarvis is accustomed to, as he wooed Nick Hayden to almost sign with Yamaha, only to see the American lost to Honda. given ex-Honda man Rossi's win yesterday, Jarvis is probably the happier today than he's been in years.

Rossi has always had a abrasive relationship with Honda, dating back to the days when they courted him into leaving Aprilia—saying that he had some time to think about their offer but if his answer was no, he would never ride for them in his life. Rossi leaving Honda shows a rebel attitude that, let's face it, all motorcyclists are familiar with.

Multitudes of people—and riders—get lost in the technical aspect of motorcycle racing, feeling that they're just an offset change, gearing swap or one click of the suspension away from set-up nirvana, or they drown themselves in despair because they're not on the best bike on the grid. Rossi's win yesterday in South Africa defies of all of that. Was he on the best bike on the grid? No, and the engine configuration (a variation of the 1990s Big Bang 500 concept) he raced had never been real-world tested, so much for optimum set up. Rossi did it on talent, luck and skill.

Also noteworthy is that Rossi—and Yamaha's—win certainly goes a long way in showing that it's a brand new day where Yamaha's GP effort is concerned. For years, almost a decade really, they have been pleased with (hopefully) a few GP wins a season and seemed comfortable being the also-ran in GP. Rossi's win may be only a single win, but would anyone bet against him winning again and again on the Yamaha this season?

If you don't believe that Rossi's win yesterday was based on talent, bravery and skill, perhaps scrolling down the finishing order for the next Yamaha finisher will enlighten you. Rossi's trio of team-mates finished 9-10-11, the fastest of them 36 seconds back.