It was another reminder of Mo'unga's extraordinary vision on attack because seconds earlier it was his cross-kick which had sent the other wing, George Bridge, upfield on a 40m run to put the Crusaders in position.
Dressed in the Crusaders' alternate white strip, Mo'unga was a malevolent ghost as far as the Bulls were concerned because while his first try was a little fortunate – the result of a favourable bounce from an excellent Bridge kick – the No10's second was all about his elusiveness and pace from 50m out.
The Bulls just couldn't put a hand on him and he haunted them for the rest of the match by spiriting his team around the field with absolute authority to help extend the Crusaders' lead at the top of the table.
For Crusaders assistant Ronan O'Gara, a handy test No10 himself over many years for Ireland, the key for Mo'unga at the All Blacks is to just keeping doing what he's doing.
O'Gara quite rightly doesn't believe Mo'unga, who has played nine tests to Barrett's 73, has suddenly overtaken his rival because you can't put a price on experience at World Cups.
"He just wants it. When you want it, usually things break for you. I just keep telling him he's got to keep showing up, keep putting the pressure on Beauden for when he gets back to the All Blacks," O'Gara said.
"No, you don't [make Mo'unga number one] because Beauden is playing exceptional rugby and he has so much credit in the bank. Obviously, you've got to respect that, and I respect that because that's what you are when you're a number one and you perform so well for your country over a serious period of time."
Both will obviously attend the World Cup in Japan and their selection will depend on the All Blacks' game plan and possible need to juggle the demands of fullback.
Barrett is an excellent fullback and Steve Hansen and company have shown a liking for starting him at first-five and shifting him to the back to allow Mo'unga to slot in at first-five from the reserves bench.
Mo'unga, who at 24 is three years Barrett's junior, is an excellent agenda-setter but can create real impact off the bench, too. Whatever the combination, the All Blacks will have two of the best playmakers at the World Cup providing the pair remain fit.
"What you need to win a World Cup, is you need two really good guys in the same position," O'Gara said. "Richie offers that, and obviously Beauden has the capacity to play other positions, as well."
Thankfully for the Crusaders and All Blacks, loosehead prop Joe Moody, who left the field against the Bulls with a cut knee, shouldn't be out too long or possibly at all.
"He's sitting up and he's in good form," O'Gara said. "It's a nasty gash that's been stitched. Hopefully, it should be straightforward enough if it doesn't get infected, but you just don't know what got into it.
"We're hopeful that over a period of time he will be available quite soon. He's hard, so he will look to play [next week]."
