Port's 15.12 (102) to 10.12 (72) victory in an AAMI Stadium trial match didn't overly faze Longmire, but he conceded the Swans were well shy of producing their renowned competitiveness.
"We need another two weeks of strong training to make sure we are competitive," Longmire said.
"We know we need to sharpen our focus for round one.
"We got some more game time into some players that really needed it for round one. It was more about getting those blokes into the swing of things than the younger blokes."
The Swans were well served by prime mover Josh Kennedy (34 disposals), Nick Malceski (25 possessions) and Jarrad McVeigh (23 touches) but Lewis Roberts-Thompson was benched when complaining of a tight calf muscle.
Sydney couldn't counter a Port side powered by new captain Travis Boak, who was best afield with 29 disposals, including 14 contested possessions. He also kicked three goals and laid six tackles.
Boak's midfield colleague Brad Ebert (25 possessions) and utility Justin Westhoff (23 touches, nine marks) were also influential.
Port led by seven points at three-quarter time and booted four goals to one in the last quarter to log another win, a week after downing another of last year's finalists, West Coast.
But coach Ken Hinkley was uncertain what could be gleaned from his first pre-season in charge of the Power.
"NAB Cup form is hard to know," Hinkley said.
"All we can take out of it is to know that we have had a real solid pre-season and we look forward to round one.
"We have a good healthy list that seems to be in reasonably good form.
"I was really proud of the boys the way they played against a really strong, seasoned side that is known for its tackling."
Port Adelaide forward John Butcher suffered a suspected broken bone in a hand in his first AFL outing this pre-season.
Scans will determine whether the injury keeps Butcher out of their March 31 premiership season opener against Melbourne.
The Swans begin their premiership defence on March 30 against Greater Western Sydney.