Ferrer will meet Germany's Philipp Kohlschreiber in the final.
Ferrer has the chance to match the record of Australian great Roy Emerson by winning the Auckland title four times, including three straight championships.
Second-seeded Kohlschreiber had a tougher task to reach the final, having to handle the powerful serve of fourth-seeded American Sam Querrey before winning 6-4, 7-6 (2).
Kohlschreiber will be attempting to win in Auckland for the second time after taking the 2008 singles title.
Ferrer's path to the final was eased by the fact Monfils had to battle another of the injuries that have recently affected his career.
Monfils' ranking dropped to 99 during 2012, as he had a series of injury setbacks and he needed a wild card to make the Auckland main draw.
"It was bad luck for Gael," Ferrer said. "He was tired after the match yesterday (against Haas)."
Monfils' injury does not appear likely to threaten his Australian Open run.
"David is an incredible player, and today I was very tired," Monfils said. "Against a player like that, he's very powerful and it's very physical."
Kohlschreiber broke Querrey in the third game of the first set and took the set in 26 minutes. After a service break apiece, Kohlschreiber swept to a 6-0 lead in the second set tiebreak and closed out the set in 42 minutes.
"I have to say, it was a really great match from my side," Kohlschreiber said. "I played unbelievable."