Henman, 31, showed considerable class against the Spanish teenager, but he lacked consistency and was ultimately overpowered even though he held the advantage early in both sets.
The French Open champion led 5-3 and held four
After a tiebreak in which Henman managed to earn just one point Nadal had to resist three break points at 1-1.
He then broke Henman to love with a forehand winner that grazed the sideline.
After holding to love, Nadal broke for 5-1 when Henman netted a forehand and Nadal closed out the match with his ninth ace.
Russia's Mikhail Youzhny reached his first semi-final of the year and a possible meeting with world number one Roger Federer when he overwhelmed Olivier Rochus of Belgium 6-3, 6-1.