In some respects yesterday's game was over in the first half when the hosts surged to a 3-0 lead as Waitakere looked like anything but the giantkillers who had toppled Auckland City 1-0 in their opener.
Bay United struck in the first minute when Barbero latched on to a Ross Willox drive, which had clipped the right-hand upright before ricocheting across the face of the goalmouth, to casually tap it into a gaping net for a 1-0 lead.
In the 19th minute, right-wing back Kohei Matsumoto made it 2-0 when he became the beneficiary on the far post of a Fergus Neil cross after a swag of players from both sides missed the ball.
It was Barbero again in the 32nd minute, dutifully following up to make it 3-0 after Waitakere goalkeeper Pirmin Strasser's sliding body deflected a Sam Mason-Smith shot.
The Reds pulled one back to 3-1 through Julyan Collett in five minutes of added time.
Barbero thought the team's attention to detail in training, coupled with precise drills on a daily basis, were paying immediate dividends.
"We've also been working on our defensive shape too," the Argentinian said, revealing they would make more strides to becoming clinical under coach Brett Angell once the new faces come to grips with each other's strengths.
The plan, Barbero revealed, was to blitz Waitakere in the first half and then "keep our shape" in the second spell as the visitors changed their formation to push more players to the coalface to try to haul back the yawning deficit.
"Brett told us not to switch off so we were [switched on] except for the last few minutes when they scored one."
In the 47th minute, Waitakere midfielder Ryan Tinsley was stretchered off for a suspected fracture of the tibia while Neil collected a yellow card.
St John Ambulance staff gave Tinsley some laughing gas and pain killers before wheeling him off to hospital.
Waitakere coach Chris Milicich said for the first half hour his troops were "non-existent", leaving him wondering if it was a hangover from the first-round highs.
"We were all over the show in that first 38 minutes and Hawke's Bay deservedly took a 3-nil lead but I think in the second half we sorted a lot of things out and were back to 3-1 but we missed a bucketload of chances," Milicich said, lamenting his team's inability to find the net more often.
The Bay, who looked sharp with every player contributing immensely, play away against Eastern Suburbs this Sunday before hosting Team Wellington at Petane Domain on November 6 at 1pm.