Pedro de la Rosa believes that HRT has already derived "a small step forward" from its new floor despite the nature of the Singapore circuit making it difficult to get the best out of it.
The Spaniard and team-mate Narain Karthikeyan both tried the new floor in Friday's second free practice session.
But the bumpy circuit made it difficult to gather quality data on the performance of the upgraded car.
"It looks like it's a small step forward, but we were not expecting to have a massive revolution in the car because it's only the floor," de la Rosa told AUTOSPORT.
"We cannot quantify how much it is worth yet because the data is of poor quality because the track is so bumpy so it's not the best place to analyse aero. We've done some cruise control runs at 240km/h but it's just so noisy.
"We need to analyse the data more deeply and learn as much as we can, but I'm not really concerned about the floor because it should be a few tenths quicker."
De la Rosa admitted that HRT does have concerns about cooling in the race, which could make it difficult to reach the finish.
"We need to get on top of the brakes and the cooling," he said. "It's going to be marginal for the race, because it's running very hot and we have to make sure that we can make it to the end.
"It's going to be a long race and people are going to suffer a lot from rear [tyre] degradation, so it will be quite a strategic race."
De la Rosa will have to take a five-place grid drop in Singapore after a gearbox change was made before final practice.