In tip top shape after a three-month camp, Duddy came out with guns blazing and needed just a minute and 55 seconds to end the scheduled eight-rounder.
He tagged Astorga with a quick one-two and then landed a stunning right to the temple that after a few seconds forced the Chihuahua native to take a knee.
"Delayed reaction," Duddy trainer Harry Keitt, later explained. "It doesn't matter how good your chin is, if you get hit hard on the temple, you're going down."
Referee Wayne Kelly gave Astorga [now 14-4-1, 9 KOs] a mandatory eight-count and when the bout resumed, Duddy patiently stalked his man.
The Mexican was backed into a corner where he took several shots including a hard left hook to the midriff that put him down grimacing.
"Once I hurt him, I caught him with a great left hook to the body," said Duddy, ranked 12th by the World Boxing Organization [WBO]. "We worked on body shots in the gym."
Kelly didn't bother finishing the count as he waved the contest over, granting Duddy [28-1, 18 KOs] his first knockout win since he stopped Prince Arron in Dublin six fights ago.
Neither Duddy, who hardly took any punishment, nor Keitt imagined it would be that easy. But neither man was complaining.
"I'd have loved to have more time but you can't knock [such] a victory. It's a good start to the year," said Duddy, who returned to Gleason's Gym two days later and is now scheduled to appear on the Manny Pacquiao-Joshua Clottey undercard at Cowboys Stadium in Dallas, March 13.
"I didn't think it would be that easy but I was hopeful that it would be," said Keitt, who's credited for his charge's return to form since their reunion last fall. "The hard work put in with John made it easy."
What pleased the trainer more than Duddy's rediscovered power was his demeanor in the ring. "John was totally relaxed and moving easily and fluidly. That's what I was looking for," Keitt remarked.
"I felt very relaxed and very comfortable in there," Duddy concurred. "Everything was flowing."
He applauded his fans for the ovation he received at the 5,600-capacity Theatre, on a show that featured two world title bouts. "It's unbelievable. I'm looking forward to doing it again," said Duddy.
DALLAS
Barney Moore of Duddy Boxing confirmed that Dallas would be the Derry Destroyer's next stop, although there's no opponent yet.
"It's the start of a busy year. We're looking forward to fighting in Texas on March 13 on the Pacquiao-Clottey undercard," he said. "John gave fans what they needed tonight. It's a great way to start the year."
PROUD DAD
There were also kudos from Duddy's dad Mickey, a former pugilist himself and his son's first trainer.
"Fantastic!" exclaimed Mickey Duddy, who flew in from Ireland. "His demeanor looked good when he came out and I expected a good performance. The old John Duddy is back."
The elder Duddy was delighted that his son had teamed up with Keitt again, saying it was a good move.
O'CONNOR FLU KO
The flu bug kayoed Danny O'Connor's fight with Canadian Darelle Sukerow in Boston last Friday.
"I'm definitely disappointed because you train, you get ready for something, and circumstances out of your hands prevent you from fighting," O'Connor, a 10-0 [3 KOs] welterweight, told local press. "It's a letdown, but my health is my number one concern. I'll come back from this."
