Hamilton produced a superb display in qualifying to secure pole position for Sunday's race and Whitmarsh revealed his delight at the Brit's form.
"He's been doing a great job all weekend," Whitmarsh told Sky Sports News. "He came absolutely determined to get a win here. We've underperformed for two or three races, that hurts everyone including Lewis, so I think this weekend it's absolute determination.
"He's been doing a great job and the car's not too bad I think either. But I think Lewis in particular is doing a fantastic job."
Hamilton has agreed to join Mercedes at the end of this season.