While the Eagles matched Geelong early on Sunday at Norwood Oval, ultimately the Cats were able to go up a gear and easily beat them by 46 points.
Reid was solid in the midfield but was taken off late in the game after giving away a free kick.
"Harley let himself down in that area today and he knows that," McQualter said.
"That was not the way we want Harley to play.
"But I also thought he had parts of his game that were strong.
"We want to make sure his discipline doesn't tip over."
The Eagles also gave away two 50m penalties that resulted in Geelong goals.
"We let ourselves down today in that part of the game. That was disappointing," McQualter said. "We can't afford to be undisciplined."
The Eagles coach noted that once the Cats took control, they were too strong in contested play.
"Pretty much every contest metric you look at, they got a hold of us as the game went on," McQualter said.
"It just overwhelmed us today by the end, a little bit - a great lesson for our guys to go through."
Jobe Shanahan's four goals were a highlight and ruckman Bailey Williams had seven clearances in his first senior game this season.
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