Adrian Sutil says that Force India is simply too slow to compete for the top 10 in Singapore.
Sutil made it through to Q3 on his last appearance at Marina Bay in 2011 but could manage only fifteenth place on Saturday evening.
"P15 is disappointing because it’s some way off where we were aiming to be," said Sutil.
"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."
Team principal Vijay Mallya believes that Force India has not been able to get the car working this weekend.
"Singapore has traditionally been one of our stronger tracks, but for various reasons it’s not suited us this year," he said.
"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."
"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."