Nadal, the defending champion, reached his first clay final since winning in Rio de Janeiro in February with a 6-4, 6-4 win against countryman Roberto Bautista Agut.
Ferrer saved nine match points before Nishikori ultimately overcame his late nerves for a 7-6 (5), 5-7, 6-3 victory that propelled him into his first Masters series final.
Earlier, Maria Sharapova held her nerve to reach her second consecutive women’s final, where she will play Simona Halep.
Bautista Agut, playing in his first career Masters series semifinal, couldn’t match the experience of Nadal, who continues to improve after coming to the Magic Box center having lost at consecutive clay tournaments for the first time in a decade.
Nadal took advantage of Bautista Agut’s timid start to break right away for a lead he would never surrender.
Nadal’s concentration dipped temporarily in the second set as Bautista Agut clawed to within 4-3 before Nadal overcame his 21 errors by pulling away to reach his 90th career final.
Sharapova was cruising against Agnieszka Radwanska before allowing the third-seed to break back in the second set. But the eighth-ranked Russian recovered to secure a 6-1, 6-4 win after Halep rallied in the hot conditions to dispatch 2011 champion Petra Kvitova 6-7 (4), 6-3, 6-2.
Sharapova has lost just three times on clay since the 2011 French Open.
Kvitova looked on course for victory before unforced errors and the rising temperatures took their toll.
The Czech was 2-0 up in the second set and rolling against Halep, who was visibly frustrated after a late call went against her during the first-set tiebreaker.
But Kvitova hit 66 unforced errors and that inconsistency caught up with her as Halep recovered, with the now composed Romanian hitting 22 winners and breaking Kvitova four times over the last two sets.
“I just started to play more angles, more higher the ball, and just fighting for every point,” Halep said.
Kvitova struggled in the final set, looking sapped of energy by the end of a match that lasted more than 2 ½ hours.
“Tomorrow I expect a very tough match. Maria is a champion and she knows how to manage the finals,” said the fifth-ranked Halep, who reached her first Masters series final.
Sharapova hit 28 winners to four for Radwanska, who netted a forehand on match point to be broken for a seventh time.