Former U.S. Open champion Del Potro fired down 11 aces and did not face a break point during the one hour, 33 minutes match.
The 29-year-old second seed, who won the Auckland tournament the last time he played in it in 2009, will now return to the top 10 in the ATP rankings on Monday for the first time since August 2014 after struggling with injuries over the past few years.
Waiting for Del Potro in the last four will be Spaniard Ferrer, who brushed aside ATP NextGen Finals champion Chung Hyeon of South Korea 6-3 6-2.
Ferrer is yet to drop a set in Auckland and has shown glimpses of his old form that saw him win the tournament in 2007, 2011, 2012 and 2013.
“I tried to play consistent and aggressive because with Chung, he plays with power, and it’s never easy,” Ferrer said in a court-side interview. “He has a really great future.”
Ferrer’s countryman Roberto Bautista Agut will play Dutchman Robin Haase in the other semi-final.
2016 champion Bautista Agut defeated Czech Jiri Vesely 7-6(1) 6-2 in the last eight while Hasse beat Peter Gojowczyk of Germany 6-4 6-4.
The fifth-seeded Bautista Agut, 29, earned an early first-set break before holding off a Vesely fightback to win the tiebreaker and take the set.
He then blitzed the second set, unleashing his trademark ground-stroke game with relentlessly accurate shots.
He also won more than 60 per cent of Vesely’s second-serve points, demonstrating the big Czech’s reliance on his powerful first serve.
Bautista Agut, the world No.21, will go on to face Robin Haase in Friday’s semi-finals after the Dutchman’s defeat of giant-killing German Peter Gojowczyk 6-4 6-4.
A potential final against Juan Martin del Potro awaits.
“Today the conditions were difficult and he was a difficult opponent, serving very well and a lefty, playing with a very flat backhand,” Bautista Agut said.
“It was tough at the beginning, to have rhythm with the ball.
“I served really well in the second set and I tried to play aggressively with my forehand, and I think I did it.”