Sergio Perez described Force India's free practice performance as "not good enough" after a difficult first day at the British Grand Prix for the Silverstone-based Formula 1 team.
The Mexican was only 16th fastest in the quicker second session on Friday, while team-mate Nico Hulkenberg, who sat out the first session for reserve driver Daniel Juncadella, was 17th.
AUTOSPORT's 'Friday Form Guide' analysis of raw pace put Force India ahead of only Marussia and Caterham, while examination of its long-run pace (usually a Force India strength in 2014) placed it well behind the other Mercedes-engined runners.
Perez said it would be difficult for Force India to repeat its form of recent races, where it has used alternative strategies to compete for strong points finishes.
"It's been a tough day," Perez admitted.
"We expected that Silverstone was going to be a difficult one for us, but it was more difficult than expected, and really not good enough.
"A lack of downforce and the wind is hurting us quite a bit. You need a lot of efficiency in your car around this place and we don't have that at the moment.
"We're having big issues with the car, big inconsistency, so we've got a lot of work ahead of us to try and solve it.
"To use alternative strategies you need pace and at the moment we don't have the pace so it's going to be a difficult one. A few points will be a great weekend for us."
Team-mate Hulkenberg said the blustery conditions in the afternoon had further compromised the VJM07.
"Wind is never good for a racing car, especially when it's so gusty and so strong," he said.
"It makes it hard for the aero to stay healthy.
"I did a long run on the medium tyre but I think that was when the wind was at its peak, so it was quite tricky.
"The car was a bit unpredictable to drive with these conditions. We've got to understand a bit more and hopefully come away with the right conclusions to improve.
"I think there's a bit more to come."