Del Potro, who had not dropped a set all week, was unable to hold serve once in the first set as the Spaniard fought his way to a 6-1, 4-6, 7-5 win.
Del Potro, who sealed the Auckland title in 2009, shone in the key moments and fought off six of the seven break points Ferrer forged in a tense clash, with two games in the second set lasting nearly 10 minutes apiece. Out of sudden, Juan Martin created the only break point of the set and he defended his backhand nicely in the following point to get an error from Bautista Agut, clinching the set by 6-4 and sending the match into a decider.
"I passed really bad moments on the court and in that moment, I scream because I was very stressed", the world No.21 Bautista Agut said.
GETTY IMAGES Roberto Bautista Agut got off to a great start in the final
"I played well and I'm looking forward to doing well in Melbourne". I've been fighting a lot on the court... "I didn't expect to reach a final in my first tournament", said del Potro, the 2009 US Open champion.
The advantage in the third set went one way then the other until Bautista Agut broke del Potro to lead 6-5, then saved a break point to win the match in 2 hours, 7 minutes. "It's a good start for me", he said. I think I played very aggressive...
"Today the conditions were hard and he was a hard opponent, serving very well and a lefty, playing with a very flat backhand", Bautista Agut said. Juan Martin netted a backhand to get broken in game number 2 but he fired up his mighty forehand to get back on the track in the following game, breaking back with a volley victor and reducing the deficit to 2-1. "I couldn't play any better, but Roberto did well at the end of the match, and I made some mistakes".