And the result was the product of a perfect game plan, brilliantly executed.
"I tried to move Juan Martin around the court, played very aggressive with my return and with very high intensity," said Bautista Agut. "I had the match more under control than him. He was surviving more with his serve than with his strokes from the baseline."
Given the circumstances, the Spaniard admitted this title, the seventh of his career, was probably the most special. It's the first time he has managed a repeat triumph and arguably the toughest opponent he has beaten in a final.
"I'm very happy," said Bautista Agut. "It means a lot. Juan Martin beat me the last three matches that I played him."
Just like 2016, Bautista Agut flew under the radar here, as focus fell on del Potro and the other top four seeds, along with David Ferrer.
He was perhaps lucky Jack Sock and Sam Querrey fell early, but there was nothing fortunate about yesterday's result. He was unquestionably the best player, though del Potro stayed close until the end.
It was a strange start to the match, as del Potro couldn't get going. There was an early 32-stroke rally but that exchange was a false dawn.
After being broken only once in the entire week, del Potro dropped serve three times in the first set.
The Argentine couldn't get his game going; not his serve, not his forehand, nor his returns. The 29-year later admitted he struggled with the afternoon start, after three night matches.
"It was a very difficult match for me," said del Potro. "Today was very hard to play with this sun, this humidity and I felt it a lot at the start. I felt a big difference with the weather."
The crowd were stunned. The cries of "Vamos Delpo" — so common across the week — fell silent. Del Potro has a natural loping gait on court — he's almost never in a hurry — but the shoulders were slumped, the head bowed and Bautista Agut closed out the set in 31 minutes. Thankfully, del Potro then found something. He started the second set with an ace, then held for the first time.
Then, serving at 4-5 down, Bautista Agut began to wobble and del Potro sensed an opportunity. He gained a rare break point opportunity, the first for either player in the set, and levelled the match as Bautista Agut dumped a backhand into the net.
The third set was the most cagey of the match.
The quality increased in the final stanza, with precise volleys, audacious drop shots and crunching ground strokes all thrown into the mix.
But del Potro was never comfortable, and Bautista Agut found a chink in the 11th game to break him.
The match reached new heights in the final game, with some superlative tennis.
Del Potro caused pandemonium as he forced a break point after a lengthy rally, before Bautista Agut saved it with an ace.
The Spaniard then converted his first match point, as a del Potro backhand sailed long.
Despite the result, del Potro pledged that Auckland fans wouldn't have to wait another nine years to see him again.
"When you lose in a final it is not a happy moment," said del Potro. "But the tournament is beautiful and I am so happy to play here. I hope to come back next year ... I am really enjoying playing here in Auckland.''
