BARCELONA, Spain (AP) — Two riders, one race, one trophy.

Defending MotoGP champion Marc Marquez enters the season-ending Valencia Grand Prix on Sunday with only one challenger separating him from his fourth title.

The role of spoiler goes to Andrea Dovizioso, an Italian who trails Marquez by 21 points.

That means the 24-year-old Marquez can assure he clinches another MotoGP title if he finishes in 11th place or better.

"It has been a tough season and one race decides everything," the Spaniard said. "It will be a special race in front of my fans at a circuit I like. But in motorsport, anything can happen."

While Marquez has made Honda the top power in motorbike racing, the 31-year-old Dovizioso has been the surprise of the year. His superb season has made him Marquez's No. 1 rival and helped Ducati rebound after the maker struggled for years to compete with the likes of Honda and Yamaha.

Dovizioso, who won a title in the sport's lowest category in 2004, kept alive his slim chances of catching Marquez by winning the Malaysia GP two weeks ago. That gave both Dovizioso and Marquez six victories on the season. Since his debut in MotoGP in 2008, Dovizioso had only won two races before this campaign.

"I wouldn't have believed I'd be in this situation," Dovizioso said. "And no one watching the races expected it. That's why I'm so happy and proud of what we've achieved in this championship."

Marquez has failed to finish three races this season, but he hasn't finished lower than sixth place in the 14 races he did complete.

So Dovizioso's chances may hang on Marquez crashing out on the curves of the Circuit Ricardo Tormo.

Spain's public weather service forecasts sunny skies with no signs of rain that could complicate the track conditions for the race.

"We will see. Twenty-one points is a lot and very difficult, but it's still open," Dovizioso said. "We have one strategy: try to win. I don't feel much pressure because I know what we've done this season and I'm so happy about the results up to now."

Marquez faced a similar situation in 2013 in his rookie season in MotoGP when he entered the Valencia GP leading the title hunt ahead of Jorge Lorenzo.

Marquez handled the pressure by letting Lorenzo win the race while he carefully steered to a third-place finish that was enough to make him the youngest MotoGP champion at the age of 20.

"To finish the race is the most important thing," Marquez said. "It's not the first time I've fought for the championship here and it's difficult but I'll try to manage it the best I can. I will go out, try to find the feeling with the bike and try to enjoy the race."