Adrian Sutil has suggested that his 2013 Force India car was a "carrot" because it didn't perform to his expectations.
The German driver returned to Formula 1 after a year out of the sport and believes he did a "good job" during the campaign, but suggested that the car was difficult to work after being strong at the start of the season.
Sutil told Auto Motor und Sport: "We had every problem that you can have: understeer, oversteer, in slow corners, fast corners. You could not do much by making adjustments in the cockpit.
"Ultimately, the car is simply a carrot. Simply nothing works."