"It will take them a little while. They will continue to build and after a couple of rounds it will fall into place.
"We controlled possession pretty well which is always a key aspect of this time of year.
Let's not get carried away. It's round one and there is still a lot of footy to be played."
Barrett conceded the Sea Eagles' new halves pairing of Daly Cherry-Evans and Dylan Walker struggled to gel.
"It was never going to be a finished product," he said.
"It was the first time they had played together and it looked like that at times," Barrett said.
Brett Stewart was a late withdrawal due to a hamstring injury but is expected to be fit for Manly's second-round match with Wests Tigers at Leichhardt Oval next Monday.
Steve Matai was placed on report for a high tackle and fellow Sea Eagle Martin Taupau was also written up for a shoulder charge.
The Dogs finished the game without Michael Lichaa (knee) and Chase Stanley (leg) but Hasler said they should be fit for Canterbury's next assignment against Penrith on Thursday.
-AAP