Nico Hulkenberg doubts Force India has the resources or the budget to improve on its best-ever finish in 2016, where it beat Williams to fourth in the championship.

Force India belied its status to finish as best of the rest behind Mercedes, Red Bull and Ferrari this season despite operating on a fraction of a budget of the sport's biggest teams. That impressive form was not enough to convince Hulkenberg to stay, however, as the German opted to switch to the factory Renault for team 2017.

Hulkenberg, who has said he expects to be competing for wins at Renault by 2018, believes Force India will struggle to match or surpass 2016 in future campaigns given the nature of modern F1.

"Difficult to predict," Hulkenberg said when asked where Force India can go from this year's finish. "To move on further, to close the gap in terms of being in the mix with the top three teams, it's very difficult.

"I think they would need a bit more budget, more resources. I think the people are there, we have a very good team in place at the track but also back at the factory so I think that wouldn't stop it. It's a huge challenge and it's not easy."

Force India's best-ever season was bittersweet for Hulkenberg, as he failed to score a podium and teammate Sergio Perez claimed two -- in Monaco and Baku. Hulkenberg finished 29 points behind the Mexican driver but says he is not frustrated by the campaign as a whole.

"No regrets. Obviously there is a few events let's say, like Monaco, where we've done a mistake on the strategy side when we had a pretty good result on the table. That's probably the biggest, not regret, but the biggest frustration of the season."