For the man hailed by some as the greatest rider ever, having found a lack of opposition on the track, has now turned to other pursuits to satisfy his continual lust for fresh challenges.
Statistics are what "The Doctor" - so named because he can cure any bike's ills - is getting into. Specifically, those in grand prix racing's record books. If he wins at the Motegi circuit, he will claim his 10th success of the season, his fifth consecutive MotoGP title, his seventh overall world title (he also has one each in the 125 and 250cc classes), and the 78th victory of his grand prix career.
But even that list will not satisfy the 26-year-old Rossi, who will never replace Barry Sheene in the affections of British racegoers but is making a pretty good fist of it with his aggressive riding style and showmanship. His post-race victory laps have become a thing of legend and more than 4,000 turned up to see him in Leicester Square last March at a pre-season publicity stunt.
Rossi is now eyeing up Mick Doohan's 1997 record of 12 wins in a season, his own benchmark of 16 podiums in a year (so far in 2005 he has 11), and his own total of 357 points in a year (he could achieve 411 by the final round in Spain in November).
"The advantage we have in the championship means that I can ride at each of the remaining six rounds without pressure to try to win every race," Rossi said.
"At Motegi, as at every race, we will try to fight for the victory. Winning is the thing I like the most."
There are even more statistics that Rossi can rewrite. Britain's John Surtees, the only man to win a world title on a motorcycle and in a Formula One car, holds the record for the highest win rate in MotoGP racing.
Surtees, now 71, won 22 of his 34 starts in the 500cc class (the rules have permitted 1,000cc bikes since 2003), giving him a success ratio of 64.7 per cent.
Rossi holds only fourth place in this table, on 56.0 per cent, having won 51 of his 91 starts. But the Italian Giacomo Agostini, in second place on 57.1 per cent, and the late Mike Hailwood, in third place on 56.9 per cent, are only slightly ahead of him: if he continues his win rate, Rossi could soon burst into second place overall.
And as the official MotoGP statistician, Martin Raines, points out: "The three riders above him raced at least for some of their career at a time when there were very few competitive machines on the grid. Rossi has a much superior win rate than the next best rider from the modern era, Mick Doohan."
Raines produces another table showing that Rossi is easily the league leader in terms of the percentage of MotoGP races in which riders have appeared on the podium. He has finished in the top three in 76 of his 91 starts, a remarkable average of 83.5 per cent. The American Wayne Rainey is second on 77.1 per cent, but Agostini, Hailwood and Surtees trail in third, fourth and fifth places, with between 73.9 and 70.6 per cent.
"On this measure Rossi has outperformed all other riders in the 57-year history of the championship," Raines says.
But Rossi's greatest achievement may lie in something less tangible than results. If he clinches the championship tomorrow - all he needs is a second place - the world will fête him rather than resent him, and that is unusual when a competitor dominates a sport as thoroughly as he controls MotoGP.
Rossi has avoided ill will by continually reinventing himself. By 1999, when he was 20, he had conquered grand prix racing's 125cc and 250cc feeder classes. He then won on the wild-handling two-strokes that ruled the 500cc class until 2001. When the 1,000cc four-strokes arrived in 2002, he rapidly adapted to Honda's five-cylinder RCV machine and became the first king of one-litre grand prix bikes.
But he took his greatest gamble in 2004, when he abandoned a run of seemingly guaranteed world championships with Honda and switched to Yamaha.
This was jumping off a cliff with no parachute, no safety net, and no guarantee of a landing in a deep blue lake. Yamaha had not won the MotoGP title since 1992, and the team and its four-cylinder bike were in disarray.
But Rossi and his Australian crew chief, Jerry Burgess, produced one of the greatest shocks in motorcycling history by stealing the title from six powerless Honda riders. Even now, Rossi keeps the world buzzing: will he switch to Formula One and drive for Ferrari in 2007? If he does, will he emulate Surtees' feat?
We may have to wait longer than we think. Yesterday, Rossi denied Ferrari's claims that he is on his way. "I don't know how Ferrari knows what I'm doing next year when often I don't know what I'm doing next week.
"I am totally committed to Yamaha next year and winning the World Championship. That will take up a great deal of my time and I will not have time for Formula One testing. I've made no decisions about anything in 2007."
David Coulthard, who drives for Red Bull in Formula One, believes Rossi should grab the chance. "If he's got the opportunity, he should come and have a go. If he does, he is going to have to start winning very quickly or people will start losing interest in him. Just because you are good at one thing, doesn't mean you'd be good at another."
So is Rossi the greatest motorcycle racer ever? Burgess has an intimate knowledge of his rider's abilities. "Valentino has an exceptional understanding of race-craft," he says. "There are gaping holes in all the other players. All their efforts are put into their lap times, and there's no spare brainpower to think of other things.
"Sete (Gibernau) can follow Valentino, but struggles to pass him. Valentino wouldn't be scared to be in a three-way race with the two others in front of him. He would be confident that he could pass them both in two laps and win. I don't think other guys have that ability to attack."
This is true. But it would be unrealistic to try to create an all-time league table of riders. Hailwood raced when the lethal Isle of Man TT circuit - six more riders died on it in the Manx Grand Prix amateur events earlier this month - formed part of the grand prix calendar.
Maybe the Irish legend Stanley Woods was more heroic than today's 200mph heroes when he raced at 120mph in the 1930s on bikes with primitive suspension and brakes, on circuits lined with walls and trees?
Rossi agrees. "It's a different time, and this world changes a lot," he says. "For me it's just important to be the No 1 of my time."
That he has clearly achieved. Gibernau, the elegant Spanish rider who used to win races from Rossi, has faded this season. Marco Melandri, the 23-year-old Italian, took over as head pursuer, but has yet to win a race. Max Biaggi, Italy's 34-year-old protagonist of high corner speed, grumbles too much about his bike - even though he's got the factory Repsol Honda.
American Nicky Hayden and the Brazilian Alex Barros have been the only riders apart from Rossi to win races this year, but neither has shown the slightest indication of being able to put together a sustained championship challenge.
Rossi's team-mate Colin Edwards has started to get on the podium, but is still seeking his first MotoGP win.
So Rossi rules. But he does it with wit and charm, and he never forgets the fans. "It was important to put on a good show," he will say after winning yet another race with a last-turn passing manoeuvre that he really did not need to have risked. That just about sums him up.
Born to ride: Two-wheeled champions who would give Rossi a run for his money
Giacomo Agostini (It)
15 world titles 1966-75
Winner of 122 grand prix races, more than any other rider. Accused in his prime of having an easy career, because he rode the three- and four-cylinder MV-Agusta bikes when most
manufacturers were fielding one- and two-cylinder machines. Disproved his critics when he switched from Italian four-strokes to Yamaha's two-strokes and still won. Latin charm and looks matched his riding flair.
Mike Hailwood (GB)
10 world titles 1962-78
Won his first world championship at the age of 21. Raced cars after abandoning motorcycles and won the Formula Two title. Awarded the George Medal for bravery after rescuing Clay Regazzoni from a blazing Formula One car in 1973. After an 11-year break, he returned to two wheels in 1978 and claimed his 14th TT victory on the dangerous Isle of Man circuit in a display of breathtaking courage.
John Surtees (GB)
7 world titles 1956-60; F1 title '64
Still the only man so far to have won world titles on both two and four wheels. Tough, fearless competitor who might have taken even more Formula One championships if he had not been obsessed with engineering as well as driving, and trying to take underdog, underfunded designs to the top. Like Rossi, fuelled by a drive to constantly take on fresh challenges.
Mick Doohan (AUS)
5 world titles 1994-98
Dour Australian destroyed the opposition both mentally and with his blazing talent on the track. Came back from almost losing a leg in a crash to continue piling up a total of 54 grand prix wins from 137 starts. In 1997 he set records for winning the highest number of races in a season, the most pole positions (12 in each case) and the highest number of points - 340.Reuse content