The plan with Black is that he will start for the Hurricanes, and then fly to Italy to join the team on Saturday, though Auckland's Mitch Hunt will likely suit up at first five in New Zealand's opener against Scotland in Parma on Wednesday morning.
MacDonald was impressed with Black's mature display against the Blues last weekend and has no qualms about the Manawatu Turbo's ability to direct this talented Under 20s outfit around the park.
"I think if he gets on the plane safely, then the whole coaching group will breathe a sigh of relief," said MacDonald.
The Under 20s won their last hit-out, narrowly, by two points, against the Chiefs Development XV, on Monday in Mt Maunganui. They were put under pressure and emerged with no bad injuries and with a better understanding of the intensity required.
"We didn't play as well as we had hoped, but the Chiefs were very spirited and got stuck into us. It was perfect preparation for the World Cup. They came at us hard at the breakdown and with heaps of line speed, and some guys hadn't experienced that before," said MacDonald.
"We were probably a bit guilty of having one foot on the plane, so we didn't bring the intensity."
But in general the preparation has been much better than in previous years, when the side has often travelled to the tournament with only one or two matches under their belt. This time they have had four, including three matches on the Gold Coast a few weeks ago, where they defeated Japan, Samoa and Australia to win the inaugural title.
"We've brought new players in and we feel like we're more battle-hardened. I thought we played really well against Australia and scored some good tries. Our set-piece was strong."
Auckland's Vince Aso is nursing a shoulder problem, but there is a heap of versatility in the backline to cover for any niggles.
Kickoff against Scotland is at 6.30am NZT next Wednesday.