Force India's difficult mid-season slump in performance continued in Singapore on Saturday, with Paul di Resta failing to progress through at the end of Q1 and Adrian Sutil only managing two places further up the grid in 15th place during Q2.

Despite that, di Resta said he'd once again do everything that he could to fight back from qualifying adversity.

"It's a tough, long race ahead of us and it's difficult to overtake, but anything can happen and we will keep fighting," said the Scot.

As for what went wrong, di Resta was blunt: he just wasn't fast enough on Saturday.

"I think we simply didn't have enough speed today and all weekend I've been struggling with my one-lap pace," he admitted. "I think we are more optimised for the race and the speed looks better over long runs, with low degradation of the tyres.

"But we've got some work to do tomorrow if we want to be fighting for points," he added. "We came here and tried to replicate as much as we could from last year, but we've just not been able to find the zone."

Sutil was no happier with his own qualifying, even if he had made it into Q2.

"P15 is disappointing because it's some way off where we were aiming to be," he said. "We are just too slow to fight for the top ten at the moment and everyone is working hard to try and understand where we are losing out.

"All we can do is keep fighting tomorrow and if we do a good strategy we can hopefully gain some places," he continued.

Force India's team principal Dr Vijay Mallya was puzzled at why a track that has been traditionally strong for the team had suddenly proved to be such a tough nut for them to crack in 2013.

"Singapore has traditionally been one of our stronger tracks, but for various reasons it's not suited us this year," he mused. "We've not been able to get the car in the optimal working range and it's clear that we are not getting the most from the tyres.

"There's a big task facing us tomorrow if we want to come away with points, but history has shown that the Singapore Grand Prix can be an unpredictable race," he pointed out. "Our long run pace has looked more encouraging so hopefully we can exploit that tomorrow and make the most of events in the race to maximise our strategies."