The lead took the sting out of the game and Cardiff tried to get themselves back into it with Ross McCormack, back for his first start in almost three months for suspended top-scorer Michael Chopra, lifting the ball over the bar from the edge of the box.
The hosts should have gone into the break 2-0 up but Nani wasted a glorious opportunity on the stroke of half-time, lifting the ball over Green but also over the bar from close range after a stunning clipped pass from Giggs.
