The first half effort had revealed the Blues had the ability to mix it with the best teams, the Chiefs were ranked second favourites in some quarters to take out the competition, and they would take confidence from that, but there was still a lot of work to be done.
MacDonald said: "We showed today that we're a good team when we get it right and we've just got to make sure we get it right for longer periods of time.
"We were obviously pretty optimistic at halftime. We played well, we dominated possession and I thought our defence looked pretty rugged so there was a lot to smile about going into the sheds."
Two things happened in the second half.
"I thought they played particularly well and I thought the impact of the bench, [first five-eighths Aaron] Cruden in particular, was outstanding. You could see the old wise head take control and on the flip side of that our error rate was too high and we just kept feeding them opportunities really," MacDonald said.
"A lot of their tries came off our mistakes.
"It's frustrating, we looked really good there and we had the wind in the second half and were unable to capitalise," he said.
There were times when they appeared to be doing it too easily, but then turning around and not continuing in the second half was something the side didn't want to be doing too often.
"If we get a lead like that it is important we do the job in the second half.
We'll be real about that, review it properly and make sure that it's front of mind and something we need to rectify," he said.
The scrum had reflected the switch in momentum in the game with the Blues dominating the first half and the Chiefs the second.
"I thought they played some really smart rugby and ended up pinning us down in the corners. Their maul was very strong and we struggled to cope with that and our goal-line 'D' was a work-on for us," he said.
The loss wasn't helped by potentially serious injury setbacks for prop Alex Hodgman and hooker Ray Niuia.