0735 GMT January 20, 2019
He will bid for a record 31st ATP World Tour Masters 1000 title against Roger Federer.
Nadal overcame a dogged effort from Marin Cilic to secure the semifinal victory 7-5, 7-6(3), reaching his 111th final and 10th of the year, atpworldtour.com reported.
It marks the fifth time in his career that he has contested at least 10 title matches in a single season.
"Very happy. Of course I played I think a very high level of tennis," Nadal said.
"[It] was a great match again. He [Cilic] played well, too. Was a great, good quality of tennis this afternoon."
"We are at the highest level of our sport, so nobody wins easy," the Spaniard added.
"If you want to compete in the most important events of the year and try to go for the victories, for sure you're going to have tough matches, and today was one of them."
With the victory, the 871st of his career, Nadal moves past Andre Agassi for solo sixth place on the Open Era wins list.
Federer had to bounce back from one set down to beat the Argentinian Juan Martin del Porto 3-6, 6-3, 6-3 in just under two hours.
With rain falling, the roof was closed for the second semifinal, in which del Potro was able to participate after a test on the wrist he injured during victory over Viktor Troicki in the previous round.
Federer claimed a key early break in the decider and, as del Potro began to show signs of fatigue, he meticulously maintained his advantage to complete a 17th win in 23 matches against the Argentine.
He now turns his attentions to Nadal, who holds a 23-14 record over him.