Seeded eighth, former Wimbledon finalist Nalbandian has struggled for much of 2008 but has often performed well in the closing weeks of the season and looks to be rediscovering his best form again.
"I played almost perfect," he said. "I think I return really well and that's important indoors."
Nalbandian will face Nikolay Davydenko in the last four after Rafael Nadal pulled out with a knee injury, while second seed Roger Federer earlier withdrew ahead of his match with James Blake because of a stiff back.
Blake will next face France's Jo-Wilfried Tsonga, who beat Andy Roddick 5-7 6-4 7-6 (7-5) in the evening match in Paris.
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