Rossi is the sport's most recognisable and, until recent events, most respected figure.
A seven-time world champion in the top category, should he seal another championship in the final race of the season in Valencia next weekend he will join compatriot Giacomo Agostini as the most successful rider of all-time.
Yet, in the face of history, his credibility has suffered after he sensationally kicked Marquez off his bike at the Malaysian Grand Prix last weekend sparking a sanction that will see him start from the back of the grid in Valencia should an appeal to the Court of Arbitration for Sport not succeed.
Whilst he is coming to blows with Marquez, it isn't even the two-time world champion Rossi is fighting with for the title. Instead it is his Yamaha teammate Jorge Lorenzo who lies just seven points back ahead of the title decider.
Rossi's gripe with Marquez is that he believes the latter has been deliberately trying to sabotage his title bid to help his compatriot.
“He would prefer Lorenzo to win. He is angry at me for a personal matter,” Rossi said after the Australian Grand Prix last month.
“At this point, the lesser evil is for him is for Lorenzo to win.”
A week later in Malaysia it exploded into an even more personal battle.
“I have lost respect for him,” Marquez replied. “After an action like that he doesn't deserve to be champion.”
For two football mad nations, the clash between two champions and idols in their respective countries has seen motorcycling dominate the sporting landscape for the past week.
Predictably, the response has been split down partisan lines with even the Prime Ministers of both countries getting involved.
“In sport as in politics, not everything is premissable,” Spanish leader Mariano Rajoy posted on Twitter.
Meanwhile, his Italian counterpart Matteo Renzi took time out of a diplomatic visit to South America to phone Rossi to offer his support.
Lorenzo was caught in the crossfire when he had to deny a report from Italian newspaper La Reppublica that he and Marquez had agreed a pact to work together against Rossi in Andorra in September.
By contrast, the coverage of Rossi in Spain has been scathing, comparing his kick out to the violent elbow in the face from Mauro Tassotti that bloodied now Barcelona boss Luis Enrique in a bad-tempered World Cup quarter-final between the two countries in 1994.
The standoff escalated on Friday when two Italian journalists were involved in a scuffle at Marquez's home in the Catalan town of Cervera.
Marquez's team reported the intrusion to the police claiming he had been subjected to insults and humiliating behaviour by the reporters.
Yet, the Italians Stefano Corti and Alessandro Onnis said it was their cameras that were broken with their TV station issuing a statement on Saturday saying a legal case would be pursued against Marquez and his family for “assault, slander and theft.”
The president of the International Motorcycling Federation Vito Ippolito described the situation between his two biggest stars as “poisonous” for the sport.
Yet, it is hard to argue that the extra spice has converted an already thrilling championship finale into arguably the most anticipated race MotoGP has ever known.
Should Rossi land the title at 36, six years after his last, he will once again be the king of Italian sport.
If he throws it away for losing his head with MotoGP's golden boy, it will be Spain that rejoices as much at his misfortune as Lorenzo's success.