Force India does not regret switching its development focus to its 2014 Formula 1 car early this season even though it is now struggling to score points.
Deputy team principal Bob Fernley accepts that Force India is now under threat from Sauber for sixth place in the constructors' championship and believes the change of Pirelli rubber at the Hungarian Grand Prix is the main reason for its struggle.
"We did all the right things to be ahead of the game and circumstances want against us on something that we couldn't control," Fernley told AUTOSPORT.
"The plan is absolutely in place for the 2014 programme, so there is no deflection from that.
"It's just a bit frustrating when we had such an incredible start and expected to be able to continue it.
"We believed we were capable of challenging for fifth place [in the constructors' championship] and to find that we are now desperately trying to defend sixth is disappointing."
Fernley believes it would have been impossible for the team to account for the tyre change, which followed a spate of failures at the British GP.
He pinpointed Force India and Ferrari as the teams most badly hit by the change.
"At the point that we made the decision to go to the 2014 car, we did it on the basis that we had performance in hand," said Fernley.
"All of a sudden to lose that and go backwards is very hard to reconcile.
"There is not an awful lot we can do about it and it's the same for everybody.
"But without doubt, Ferrari have also had a hit in the same way that we did.
"Lotus seem to have recovered better but certainly Ferrari and Force India have been badly set back by the tyre change."