Nadal, who had been sidelined for seven months while recuperating from a knee injury, came close to pulling out a victory last week in Vina del Mar in his return from the layoff, but fell to Horacio Zeballos in the final.
This week in Sao Paolo, however, the Spanish superstar proved he's all the way back from the injury, dispatching is Argentinian opponent 6-2, 6-3 for his 51st career title.
It marked the second time Nadal won in Brazil, but his first since 2005.
Nalbandian, meanwhile, fell to 11-13 all-time in finals and 2-5 against Nadal in his first meeting with him since 2007.
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