Maybe the nerves won't be as great, because I'm in the final already."
McCartney said her lack of vaulting in the last month may have caught up with her.
"I was struggling to control my legs, they went a bit jelly and were doing some strange things.
"It wasn't ideal, but I made it. So I'll count my lucky stars."
Zane Robertson finished 16th in the 10,000m final, 58.92s behind winner Mo Farah.
Robertson didn't speak to media afterwards, despite being a carded athlete eligible for $30,000 in taxpayer funding through performance enhancement grants. It's understood he had suffered some cramping in the hips.
Joseph Millar advanced to the main round of the 100m, running 10.29s to finish second in his preliminary race, but could not progress further.
He finished fifth with a time of 10.31s in his heat, 0.07s outside qualifying as one of the six fastest outside the top three in each heat.
"I'm not quite happy with the time I ran, but there was a lot more things happening around me.
"Getting down in the blocks, the crowd went quiet and someone called out 'go Kiwi'. It chucked a smile on my face, and got me good and ready to go.
"It's all been learning for the 200m later on, and then the bigger target of the Commonwealth Games next year."
Discus thrower Marshall Hall failed to reach the final. His 56.64m effort left him 7.86m short of the automatic qualifying mark.