The Power were blown away in a match-winning opening term from the Swans, who piled on eight goals to one to lead by 43 points at the first change.
The visitors recovered to virtually match the Swans on the scoreboard in the second half, but all the damage had been done in the first 25 minutes.
The Port Adelaide players were second to the ball and allowed the home side too much room to move on the tight SCG.
Cassisi, who racked up 21 possessions (nine contested), four clearances and seven tackles, was one of few Port Adelaide players that could hold his head high after the 55-point thrashing.
Assistant coach Matthew Primus said the impromptu morning session had been Cassisi’s idea.
“It’s part of why Dom was chosen to lead our club,” Primus said.
“The first quarter effort was really unacceptable. There’s always a penalty when you produce something like that, and that’s what this morning was all about.
“The players had a chat and did some stuff in the pool for quite some time. I think they did about 100 laps, so lucky it’s only a 25-metre pool.”
Primus admitted the coaching staff had no idea why Port Adelaide's intensity was so sorely lacking early in the game.
“We’re reviewing the game this morning and again this afternoon,” he said.
“After quarter-time, or halfway through the first quarter, we matched them [the Swans] in the hard-ball gets and clearances. It was just that first 15 minutes [that cost us] and scoreboard-wise, it was game over then.
“We’re not quite sure why. Sydney just came out and played at a better level than us.”
The Power, who placed a big emphasis on winning contested possession over the pre-season, have improved significantly in that area this year.
Primus said he was confident the team had enough players capable of winning the hard ball.
“Last week, we matched a team that wins contested footy better than anyone else in Richmond, so it was disappointing not to be able to do it for four quarters on Sunday,” Primus said.
“[When that happens] it means the opposition are going in harder than you and are running harder than you, and that’s been our problem this year.
“At times, we’ve been up and down. We haven’t been able to get any consistency going, and we’re working our butts off to try and bring it out week-in and week-out.”
Primus said the players were keen to make amends against Collingwood this week.
“It hurt the players that we haven’t been able to string wins together knowing that, with the way the results are going, a win on the weekend would’ve separated us by a game or a game and a bit from the other teams,” Primus said.
“The players are hurting. They’re not a happy bunch in there at the moment, and they probably wish they could play Collingwood on Wednesday rather than Sunday night.”
