CHRIS Fagan could not hide his disappointment in Brisbane's first-up shellacking from Sydney on Saturday night, describing its performance as fumbly and poor.

The Lions coach was surprised by the 31-point defeat and questioned whether his players thought they had the job done by half-time after clawing back to level from a four-goal deficit.

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Fagan did not sugar-coat the performance, conceding his vaunted midfield was beaten, and ball use going forward and defensive transition was below par. 

"There’s a lot of things that went wrong tonight," he said.

"The players will be disappointed in themselves. It's not the start we were after."

Brisbane kicked the first three goals of the game and the last three, but everything in between was a sea of red and white.

When the Lions made a mistake, Sydney ran in waves and pounced.

The Swans won the inside 50 count by just 59-57 but marked the ball 23 times to five in that region, many of them uncontested.

"We didn’t defend well tonight … we were really poor in that regard," Fagan said.

"Our reaction time to defend when they won the ball wasn’t good enough.

"Whether our blokes thought at half-time 'OK we’ve matched their challenge, we’ll be right now', I’m not sure. 

"Not a good night for us but a great night for Sydney. They played particularly well.

"It's not the end of the world, but it's not ideal."

Sydney coach John Longmire was understandably delighted with his young team, particularly debutants Errol Gulden, Logan McDonald and Braeden Campbell, who all had big impacts.

"We played them thinking they could help us win and it's great we've added some more youth to our team … and most importantly they've come in to do a job and compete and all of them did that," he said.

"They were fantastic, they were really good."

Longmire said despite going into half-time level after giving up a big lead, he was more than comfortable with the Swans' position.

"We came to be in the game at half-time and you look at the scoreboard and it's even.

I was thrilled.

"(I said) 'We're right in this boys, (in it) up to our eyeballs'.

"There was a really good feeling in there."