SAO PAULO (Reuters) - Ferrari's Sebastian Vettel says missing out on the 2009 Formula One championship still ranks as a more painful moment than losing to his Mercedes rival Lewis Hamilton this season.
Hamilton clinched his fifth title, and fourth in five seasons, in Mexico last month with two races to spare. Vettel is sure to finish the year as runner-up.
"I have been three times now in a position like that with '17, '09 and this year. Probably '09 was the worst one, the lowest point," the German told reporters at the Brazilian Grand Prix on Thursday.
"You never know what the next year brings. You never know whether you get another chance," Vettel added.
"Obviously I will work very hard for it, and I am confident it will come but ultimately I don’t know. You can’t predict. None of those moments were nice."
Vettel finished 2009, his first year with Red Bull, nine points behind Brawn GP's champion Jenson Button in a championship won by the Briton at the penultimate round in Brazil.
He had to wait until 2010 for his first world title and ended up with four in a row from 2010-13 before moving to Ferrari in 2015 while Mercedes began a run of dominance.
The German was also runner-up to Hamilton last year, the first season since the retirement of Mercedes' 2016 world champion Nico Rosberg.
Hamilton has won nine races to Vettel's five in 2018 and went to Mexico with a 70 points advantage and needing only to finish seventh.
With that title decided, Mercedes now have to wrap up the constructors' crown for the fifth year in a row and will do so at Interlagos on Sunday providing Ferrari do not score 13 points more than them.
Vettel said the Italian team, still Formula One's most successful of all time, believed they could "have at least a word" in the outcome.
"We try everything we can. We go flat out and try and score more points so that’s everything we can do," he said.
"We’ve seen in the last race how quickly things can change when you struggle with tyres and so on, we’ve been on that side as well. We keep our head down and try our best.
"I still have a mission here and want to win so that doesn’t change. The last race was a tough one to swallow, and probably the winter will be as well, but giving up is not an option."
(Writing by Alan Baldwin in London, editing by Ed Osmond)