Nico Hulkenberg believes that Force India can hold off Williams in the constructor's championship despite not bringing any updates to the car.
Hulkenberg finished ahead of Pastor Maldonado in Japan, having held him off for much of the race.
Williams is currently 23 points behind Force India with five races left.
The German says that the team now has a better understanding of the set-up and how to manage the tyres despite the lack of upgrades.
"Obviously we were able to have a pretty good look at Pastor as he was pretty much behind me all race in Suzuka so we see where the strengths and the weaknesses are," He said.
"I think they are not that far ahead and we have a good package for the last five races and we should be able to fight them off," added Hulkenberg.
"We haven't brought parts now for quite a few races but it seems there are performance gains.
"It is difficult to understand but I think towards the end of the year you always understand the car better and set-up wise with the tyres it makes us look altogether more competitive," he said.