For the record, ignoring the politically correct brigade, Robertson was right in venting his spleen at the lad who does need to learn on the spot in the cauldron when spontaneity takes over set-piece play.
On the other end, schoolboy Morgan failed to put one past Wairarapa goalkeeper Matt Borren in the 15th minute for an equaliser following a one-on-one situation in the 18m box as his shot went spraying parallel with the crossbar.
No doubt Morgan could have done better a few other times but he shares the common denominator of inexperience with Underhill.
It isn't a blame game and coach Grant Hastings was the first to make that clear after the game but experience sits squarely on the shoulders of other senior members - the ones who didn't follow up Morgan's 15th-minute miss, the ball remaining in play near the corner flag, begging to be played before rival keeper Borren retrieved it.
If experience is the yardstick one could ask where does homeboy Andy Bevin, returning from his American university, sit in the scheme of things?
With the clock ticking down, substitute striker Bevin missed two sitters - one a header under no pressure and a fraction later a toe poke from point-blank range that sailed cruelly over the crossbar to leave behind a rash of what-ifs in the minds of the Bluewater faithful.
In Bevin's defence, his West Virginia University Mountaineers team employ him in a defensive midfield role so perhaps he's a little rusty in his sensible shoes.
Primarily, though, both teams played a great first half of attack and counter-attack although the Adam Cowan-captained visitors had the better passing game.
In the second half the Blues lost their structure when Hastings injected Regan Cameron in the backline, pushed striker Danny Wilson to defence but kept Morgan up front.
The Rovers' experienced ones were again tested when they started putting through long balls in the air to Morgan who had no chance of getting past burly Wairarapa centreback Waisaki Sabutu who, at will, used him as shoulder prop.
In the 77th minute, common sense prevailed when Wilson was sent back to the front to reflect some compatibility with the former Fiji international.
Hastings agreed but asked to balance that against shots they took at goal and chances his men created in the second half.
"We've eaten them up. We created chances but didn't score.
"You are not going to win games or get back into matches if you don't take those opportunities."
He felt the only difference was that Wairarapa took their chances.
Bevin, he said, had only three weeks of training but threatened enough times to give the Rovers a sniff, although other players had also missed goal chances.
In the sixth minute striker Charles-Francois Mallmann put Wairarapa 1-0 up from the deflection of a defender's foot after the Blues twice failed to clear the ball from the danger zone following a corner.
Cowan hooked a charging Argentine, Ezequiel Dondiz, in the 18m box in the 26th minute for referee Jordan Williams to award a penalty kick.
Midfielder Cole Peverley equalised from the spot kick even though Borren dived the right way.
In the 35th minute, centre-mid George Jermy pushed Wairarapa 2-1 ahead from a crisp drive just inside the 18m box as Underhill got his fingers to it but couldn't stop the ball clipping the right upright and rolling in.
In the 71st minute, ref Williams cautioned Hastings after he barked at Dale Higham from the dog box as the Wairarapa player picked up the ball for a throw in.
"Just handbags," was Hastings' response.
Two minutes into added time, amid an air of inevitability as the Rovers pushed their defenders up, striker Seule Soromon pounced on a ball from 40m out, ran down the left flank before curling it to the far post for Mallmann to rocket it to the roof of the net.
In the other games at the weekend, Petone beat Wellington United 2-1, Olympic beat Lower Hutt 2-1, Miramar thrashed Western Suburbs 5-2 and Upper Hutt crushed Tawa 4-0.
