The Roos went down to the Bombers by 39 points at Etihad Stadium on Friday night, but the margin didn't accurately reflect Essendon's dominance.
The Bombers smashed North in possessions (449-291), marks (159-73) and, most concerning for North coach Brad Scott, clearances (52-30) and stoppages (35-21).
Scott described his team's performance as "horrific" and Thompson did not disagree when he spoke with AFL.com.au after the match.
"We've had a great pre-season so to bring up a performance like that is very disappointing," Thompson said.
"We're ashamed of it obviously, it's pretty hard.
"We know what we've done wrong already and we'll work on that at training."
Thompson acknowledged North's ball movement had been poor at times against the Dons, but said its chief failing had been its inability to win possession.
"We just couldn't get our hands on it. We couldn't win the contested ball and that's what we're known for, so we're pretty disappointed with that," Thompson said.
"You've got to have the ball to move it and we didn't have our hands on it a lot.
"It all started with the contested ball. We were down a lot in that and have got to get that right first."
Thompson said North had been expecting Essendon to play the high-possession game style it employed on Friday night, but had simply been unable to combat it.
The Roos now have nine days to lick their wounds before their round two clash with the Western Bulldogs at Etihad Stadium next Sunday.
Thompson is confident that will be more than long enough for his team to rediscover their ball-winning ways.
"It's pretty easy to turn around I think. With a nine-day break we've just got to get our drive back," he said.
"I'm talking about contested ball so much. We were down a lot on that.
"If we start winning the ball, teams have to start worrying about us, not the other way around."