The experienced pair chartered similar paths this week, both showing their experience and poise to surge through clutch moments. This time, though, it will not be a young gun on the other side of the net they can exploit.
Ferrer, in his 13th appearance, knows this court and atmosphere better than anyone. Four titles make it a happy home. Confidence continues to rise after cruising past adopted crowd favourite Hyeon Chung 6-3 6-2, and he also holds a 6/4 advantage in previous matches against del Potro, who he called a friend.
The 35-year-old Spaniard, who slipped to world No 37 after enduring a difficult 2017, attempted to downplay that potentially positive omen, revealing he spends more time (two-to-three hours) recovering from matches than playing these days.
In what is expected to be his last Auckland dig, though, he has everything to play for.
"Now we are in a different moment. When I beat Juan Martin del Potro I was top 10 now the top 10 is him and not me. Now he is the favourite player to win this tournament but I will fight to be in the final," Ferrer said.
"If he takes the forehand he takes the initiative and I don't have a chance. I know I will have to play my best tennis, like today and yesterday, to have a chance to win."
Del Potro won the last two meetings with Ferrer at the 2016 US Open and Wimbledon but, within himself, Ferrer feels a different man to the past two years.
"I'm very happy because yesterday and today I played very consistent," Ferrer said. "Since two years ago I didn't play more than two matches like this without mistakes. I don't know if it is going to be like this tomorrow but I am trying to enjoy this moment.
"For me it is a surprise to play like this for these two matches."
Respect flows. Del Potro knows his big frame and long legs will need to cover more ground than he has been forced to thus far this week but he sure is difficult to counter in full flight. The Argentine doesn't get too worked up but there is a sense he, too, is building some classy form.
"We have played many times and we always have good battles," Del Potro said. "No-one cares about David's ranking because he is such a great champion of this sport. It's going to be interesting to watch and I hope to play a good match.
"It's a good challenge for me to see how my body is before an important event like the Australian Open but I am very focused to reach the final here in Auckland."
Whoever emerges should, in theory, kick on to claim the title, with either Dutch veteran Robin Haase or Spanish fifth seed Roberto Bautista Agut to contest the final.
