JACOB van Rooyen's debut has been a long time coming, but in his first outing at the top level he lived up to every bit of the hype that's surrounded him.

The 19-year-old was a first round draft pick taken by the Demons immediately after their 2021 premiership win, but he had to bide his time in the reserves last season as the Demons' older, more established tall forwards kept him out of the side.

But in front of more than 40,000 fans at the MCG on Sunday afternoon, his much-anticipated debut started with a bang – he hit up Alex Neal-Bullen with his first touch for the opening goal and booted one himself from a free kick to provide his side's second major.

When key forward Ben Brown was substituted out with a back injury, van Rooyen made the most of his opportunity in a remodelled forward line, matching Bayley Fristch and Kade Chandler with three goals, including two in the final term, and provided the highlight with a huge mark on the back of Swans ruckman Peter Ladhams.

He finished with four score involvements and six tackles to go with his three majors, drawing praise from coach Simon Goodwin.

"He was prepared to do the aerial stuff, follow up at ground level and physically be ready for the game.

"I was rapt. He's exciting for our footy club, as is Kade Chandler."

Questions arose over the Demons' ability to set up a premiership tilt when first-choice ruckman Max Gawn went down with a knee injury last week that will sideline him for more than a month.

But they were answered emphatically on Sunday by off-season recruit Brodie Grundy, who exerted his influence with 21 disposals, 25 hitouts and four clearances.

Grundy's telling contribution against Ladhams came in his third game with the Demons after injury restricted him to just six appearances for Collingwood last season.

"He was sensational (the way he) took that sole responsibility on his shoulders," Goodwin said.

"He's a different player to Max. He wins contested ball, he links up with possession and he gave us a great aerial contest when we needed it.

It was another disappointing day for Sydney at the MCG in what was their first trip back to the venue since last year's Grand Final embarrassment at the hands of Geelong.

"Sometimes you can look at different things but if you're not winning the ball and you're not tackling when they're winning it, it's not a good sign," Sydney coach John Longmire said.

"We were just a fraction off which is all you have to be against good teams."