Fernando Alonso refuses to speculate on whether Sebastian Vettel's Red Bull car has been the difference between the two men in the drivers' title race this season.
While Vettel celebrated his fourth straight Formula 1 world championship, his tenth win of the season and sixth in a row at Sunday's Indian Grand Prix, Ferrari's Alonso finished out of the points in 11th.
The Spaniard, a winner of two world titles with Renault, also doesn't know how he would have done in Vettel's car.
"I'm not here to guess, I don't have a crystal ball to see," he said. "We all feel we have the confidence to do a good job, it is impossible to say.
"Today is the day to congratulate (Vettel) and for him to enjoy the championship."
Alonso, who is second in the drivers' standings with three races left in the season -- 155 points behind Vettel -- does know Ferrari faces a considerable challenge to stop Red Bull's continuing dominance.
"It is time for us to work even harder, because we have a strong challenge ahead of us because they have been dominating for the last four years," he said. "We need to do something better because clearly we have not done enough. We'll start immediately and next year we want to win."
Alonso on Saturday said he's enjoying a "fantastic" season despite his failure to challenge Vettel.
Next season he will be joined at Ferrari by Kimi Raikkonen, who he replaced on the team in 2010. Alonso maintains that while he is flattered by interest from other teams, he's happy at Ferrari.
"For me it makes a difference to have the team happy," he said. "The rest of the teams, are more complicated, it is impossible to make everyone happy. ... Ferrari have always trained me very good. All the teams that have seen me working closely, they like my professional attitude."