AT QUARTER-time last Thursday night, nobody thought Christian Petracca was on the cusp of having a career-best game.

Limited by Carlton's Matt Kennedy through the midfield, Petracca had just four disposals in the opening term and hadn't gone near hitting the scoreboard as the Blues raced into a 30-point lead at the first change.

But his versatility in being able to go forward after quarter-time effectively changed the match as a contest. Petracca ended the match with five goals, 10 score involvements and two goal assists, helping the Dees get to within a point of a dramatic comeback.

While Petracca ranks third among Demon midfielders for centre bounce attendances this year, behind only Jack Viney and Clayton Oliver, on Thursday night he had just two involvements after quarter-time.

Instead, Melbourne left the bulk of the responsibility to Viney, Oliver, Tom Sparrow and Alex Neal-Bullen as Petracca did his damage up forward.

While Petracca might not have spent enough time in attack this season to be considered a forward by Champion Data's metrics, it put a host of other significant role changes made this season in the spotlight.

None have been more impactful than Isaac Heeney's move into the midfield. Now averaging career-highs for disposals (27 per game), clearances (6.4), contested possessions (12.9), score involvements (8.8) and metres gained (463.2m), Heeney has been huge in Sydney's impressive 8-1 start.

Last season, Champion Data notes he averaged 11.9 AFL Player Ratings points – the stats guru's most definitive way to measure influence on a game – while playing as a forward. This year, in the midfield, that has risen to 22.1 points. The increase of 10.2 per game is the most of any player to have changed role this year.

North Melbourne's Charlie Comben has the second biggest increase, having been used predominantly as a 199cm intercept defender under Alastair Clarkson this year. His Kangaroos teammate Tom Powell is third, after shifting from a half-forward role last year to a pure midfield role this season.

Elijah Hollands, having been used predominantly on a wing at Gold Coast last year, has shifted to a half-forward role at Carlton this season and has also enjoyed great success in his new position.

Meanwhile, West Coast veteran Elliot Yeo regained fitness earlier in the year and returned to the midfield – having played in a defensive role last season – but has been among the Eagles standouts since going down with a groin injury a fortnight ago.