Despite matching Adelaide in almost every statistical category at Metricon Stadium on Saturday, the Suns shot themselves in the foot with poor turnovers and lack of forward pressure.
The result was a 28-point loss, a drop to 5-8 and almost a final farewell to any chances of sneaking into the top eight this season.
McKenna described Adelaide's pressure and the SUNS lack of composure as the "perfect storm" that cost his team.
"It was terrible," McKenna said.
"Polish that kick inside forward 50, kick straight, make better decisions going forward, we win that game.
"It still wasn't our best football and I think that's how far we've come. That's a positive.
"Out of 10, five maybe. I thought our ability to put pressure on and tackle was expected, we got that, it was more the technical side going forward we let ourselves down.
"If we played at a seven, we probably win that game. We played at a five today as far as our polish goes and you get that result."
Gold Coast SUNS won the inside 50s (59-57) and tackles (46-45) and were super competitive in the clearances (34-34) and contested possessions (140-141), so its effort was not in question.
But too often Adelaide waltzed the ball from its defensive 50 and converted it into a scoring shot at the other end.
In the second quarter the Crows had 10 inside 50s and kicked 7.3.
McKenna said an All Australian back six could not stop that ball coming forward and criticised his team's forward pressure and lack of midfield spread.
However, he said it was not a trend.
"Let's not forget two weeks ago, I know the conditions were different, North Melbourne couldn’t get it out of our forward 50," he said.
"So they have done it before. Do you get that inconsistency with a young side? Of course you do. Some days it works, some days it doesn't. It's not a trend."
Although not overly impressed with Karmichael Hunt's return from hamstring tendonitis, McKenna was not too harsh on his hard-nut, who played his first senior game in eight weeks.
Hunt had two disposals through three quarters and was subbed out for debutant Andrew Boston at three-quarter time.
"We're looking for a bit more than that, that's for sure," he said.
But he saved special praise for Dion Prestia and Jaeger O'Meara, who racked up 42 and 32 disposals respectively.
"To assign a bloke (Prestia) in his third year to Scott Thompson … and Jaeger O'Meara in his first year on Patty Dangerfield, I think it says something about your faith and trust in those blokes," he said.
"And to have 70-odd possessions between the two of them was a fantastic effort."
