Top-seeded Nadal brushed aside countryman Guillermo Garcia-Lopez 6-3, 6-2 in a quarter-final that was interrupted by heavy rain for more than three hours after just three games had been played. The victory kept Nadal on course for his first ever title in a season-opening event ahead of the Australian Open, the latest edition of which starts in Melbourne later this month. The left-hander finished runners-up in Auckland in 2004 and lost in the semi-finals here last year to eventual champion Xavier Malisse of Belgium.
"The rain only delayed the match, it was not a distraction," said Nadal. "We see more rain at Wimbledon every year."
Moya, a two-time champion in Chennai in 2004 and 2005, easily disposed off unseeded Frenchman Florent Serra 6-3, 6-4 in the first quarter-final played before rains hit the Nungambakkam Tennis Stadium.
The other semi-final will feature fourth-seeded Russian Mikhail Youzhny against promising Croatian youngster Marin Cilic.
Youzhny ended champion Malisse's seven-match unbeaten streak at Chennai with a 6-4, 6-4 win well past midnight.
Cilic, 19, a former world junior number two, came from behind to oust Dutchman Robin Haase 4-6, 6-2, 6-3 in a match that was shifted to an outer court because of the late start due to rain.
The third-seeded Moya broke Serra in the fourth game of the first set and again in the opening game of the second to win in an hour and 15 minutes.
The 31-year-old former French Open champion said he was ready to face Nadal after playing his "best match" in the tournament.
"I was pretty happy with the way I played today. It was my best match so far. I served well and although I broke his serve only twice, I could have done it many more times.
"I think it will be a tough match against Nadal. There will not be any pressure on me because I have nothing to lose," said Moya, currently ranked 17th.