He enjoyed a routine win over Santiago Giraldo, maintaining his unbeaten record against the Colombian with a 7-6 (8/6) 6-3 victory to set up a meeting with Mardy Fish.
The American has enjoyed a stellar year and is pushing for a place at the ATP World Finals in London. He did his chances no harm with a come-from-behind 6-7 (5/7) 6-4 6-1 win over rising star Bernard Tomic.
"It was very tough," Fish told atpworldtour.com afterwards.
"London is the main goal at the end of the year. I have never made it before. I desperately want to, that`s no secret.
"I have had a great tournament so far but there is still work to do."
Great Britain's Andy Murray will face Nadal`s compatriot David Ferrer in the other last-four clash.
Murray, arguably the form player on the Tour with 10 straight wins, saw off Argentina`s David Nalbandian 6-4 7-5, prevailing following a run of five straight breaks of serve in the second set.
Ferrer was also a comfortable winner, beating Radek Stepanek 6-2 7-6 (6/3).