The second-half opening minute goal from Bay striker Sean Lovemore - a classic example of individual brilliance on debut in front of the home crowd - saw him beat a defender, put his foot on the gas, beat another player on the edge of the 18m box before drilling it to the bottom left corner as goalkeeper Matt Borren dived in vain.
Maybe Greatholder could have injected some of his bench players with fresh enthusiasm and valuable game time before this weekend's tough assignment at Kiwitea Street against Auckland City but the two-goal wobble might have changed his mind.
Robertson took the jab on the chin, conceding his troops could have played better.
"The first-half performance wasn't exactly where we wanted to be at so we thought we could improve on that in the second half," the centre back said.
He said while they scored early in the second spell, they were guilty of letting the opposition back into the game.
"We're disappointed with that but we know we can improve on that in the future," the 28-year-old said, adding they demanded a bit more at halftime, knowing some sloppiness was indicative of that.
"We started brightly for the first 10 or 15 minutes and then we lost shape a little bit and they started gambling a little more to create a couple of chances to score."
With no one ecstatic at the final whistle, Robertson said that was a testimony to the high standards the squad had set for themselves.
Played in idyllic spring conditions, without any wind, the game was pretty one sided despite Manawatu scoring two goals in the space of two minutes.
The Adam Cowan-captained Manawatu were far too casual in defence in the first half with some of them trying to dribble every time they touched the ball.
In the attacking third, they looked bereft of ideas, even when they were fortunate enough to have possession.
If they had beaten Otago United 3-0 in the previous opening round than it begs the question: "How good are the Southerners?"
Maybe, just maybe, the Stu Jacobs-coached Manawatu were having an off-day yesterday.
The free rein accorded to Cowan posed questions on their mind set, leaving fans confused about whether the captain was a centre back or striker, although players tended to play like individuals until the second half.
The omission of defender Nathan Cooksley from the starting line up also raised eyebrows - injecting the Wairarapa United player in the second spell made a considerable difference in that they conceded only one goal.
Bay United English import striker Stephen Hoyle drew first blood in the sixth minute with a header for a 1-0 lead following a short pin-ball effect in the 18m box after a freekick from 5m inside the Manawatu half.
Four minutes later Manawatu left wing Dale Higham, lurking on the left flank, put a ball through to striker Seule Soromon who worked it into the box but curled it over the crossbar from an acute angle when he could have pushed it with the first touch to an unmarked Josh Chettleburgh waiting 10m off the right upright.
In the 27th minute, Manawatu keeper Borren made an outstanding save from a one-on-one situation, parrying a Lovemore right-footer after Soromon causally coughed up possession at the halfway mark.
Four minutes later, midfielder Cole Peverley extended the Bay's lead to 2-0 from the edge of the 18m box as the Manawatu defenders blissfully remained in slumberland.
Jordan Martens came in for Higham, who hobbled off in the 37th minute after what appeared to be an errant foot with no malicious intent from Lovemore in a tackle.
Aucklander Lovemore, in displaying his clinical finishing skills, took the Bay to a 3-0 lead in added time of the first half with a worm burner on the right flank from the acutest of angles to beat Borren.
With Lovemore finding the net again seconds after play resumed, Bay right winger Harley Rodeka smashed a ball wide out from 25m but the ball cruelly rocked the woodwork to bounce back into play.
Youngheart scored their first goal from last weekend's hat-trick hero, striker Thomas Mosquera, in the 75th minute after some nifty passing in the 18m box.
That put a spring in their step and, controversially, substitute Lewis Cumber made it 4-2 two minutes later from another staccato of passes.
Bay ref assistant Jordan Williams had his flag up for an offside but referee Nick Waldron wasn't swayed after consulting his flag man as the Bluewater faithful heckled him into the final whistle.
In fairness to Waldron, he was consistent in flashing a yellow card to players who appealed for a foul when he didn't think so.
Coach Jacobs agreed his men "weren't even close to it" in the first half.
"You can say we weren't there but I thought Hawke's Bay defended well as a group and then picked on our mistakes and countered well so we were just off the pace."
Jacobs said the tactical and technical nous didn't matter if teams took the park without the proper attitude and application.
"We sorted it out at halftime but to take a shot in the arm straight after halftime with a goal in the net effectively killed the contest."
On the bright side, he felt his men showed character to get back into the game when last summer they would have exposed a soft underbelly.