Rubens Barrichello has denounced a "horrible" start to his 18th consecutive season in Formula One.
Williams was buoyed by a positive winter season, but the veteran Brazilian Barrichello said Melbourne and Malaysia have left him disappointed.
"It's sad, but after two trials, that is the right word. We expected a stronger start to the season," the 38-year-old told Brazilian television Rede Globo.
"I think there is potential to discover in this car, but the first two races have been horrible," he added.
Barrichello said the main problems are a lack of straightline speed and "the lack of reliability to finish the races".