Anderson, seeded 28th, beat the Spanish 12th seed 4-6 7-5 6-3 6-4 in NY.
Anderson, 31 years old and ranked 32nd in the world, is the lowest-ranked Grand Slam finalist since 38th-ranked Jo-Wilfried Tsonga fell at the 2008 Australian Open final. "It was really nice that they came out and watched me". He served 22 aces to one for Carreno Busta, with a fastest serve of 135 miles per hour.
Anderson then to served his way in the fourth set make his way into the final.
Golfing compatriots and major winners Charl Schwartzel and Louis Oosthuizen watched him win Friday on the NY hardcourts to reach the brink of a breakthrough win at 31. He didn't drop a set through his first five matches.
Kevin Anderson stretches for a backhand against Pablo Carreno Busta.
"It's been an wonderful season for me and I'm so happy to get a chance to fight for another title after a couple of seasons with injury troubles", said Nadal, who won a record-extending 10th French Open title in June.
But it is Anderson and his huge serve - he has reached 137 miles per hour during the tournament - that has come through to the final on the bottom half. "I was told I probably needed surgery on my hip", Anderson said.
Will the big-server and former top-tenner from South African have too much to handle for Carreno Busta?
Two games later Anderson saved a pair of set points, but a third was quickly snatched up by Carreno Busta as a serve out wide was returned into the net. The 2.03m tall Anderson had the golden opportunity to earn a double-break lead in the seventh game, but wasted two break points and allowed Carreno Busta to lessen the deficit instead. He committed 14 unforced errors to just one for Carreno Busta in the set.
I like Nadal to win another grand slam title. Anderson hasn't won an ATP title since 2015 and has won 28 and lost 15 matches this year.
Like any new part of his game, the methodical Anderson first worked on his demonstrativeness on the practice courts, where most players quietly go about their business. Nadal is 5-2 in his last grand slam final appearances. He attacked with blood in his eye and he defended as if his life depended upon it. Del Potro, increasingly tired as the sets flew by him, could do nothing to stop Nadal's march to the final.
Del Potro has been virtually running on empty.