Ferrer - winner of this event in 2007, 2011, 2012 and 2013 - triumphed 6-3 6-2 over Chung Hyeon to reach the last four for the eighth time in 13 attempts.

The Spaniard took 75 minutes to see off his South Korean opponent and will now meet second seed Del Potro for a place in the final.

Del Potro will return to the world's top 10 for the first time since August 2014 next week and took a step closer to repeating his 2009 win in this tournament with a 7-6 (7-4) 6-3 win against Karen Khachanov.

"We have played many times and we always have good matches," Del Potro said of Ferrer, who is ranked 38th in the world but holds a 6-4 head-to-head record over the Argentine.

"Nobody cares about David's ranking, as he is a great champion of the sport. It doesn't matter about his ranking or mine, I just think it will be a good match for the fans."

The other semi-final will see Roberto Bautista Agut take on Robin Haase after wins for the pair against Jiri Vesely and Peter Gojowczyk respectively.

In Sydney, 18 year-old Alex de Minaur continued to delight the home crowd with a 6-4 6-4 win against Feliciano Lopez and will face Benoit Paire in the semi-finals, after the Frenchman knocked out defending champion Gilles Muller.

Fabio Fognini takes on Daniil Medvedev in the other last-four clash.