He entered top-level football early when he played for Victoria at under-12 level and he represented them throughout his junior career, culminating in selection for Vic Metro in the 2014 AFL Under 18 Championships.

His achievements as a junior included winning the Larke Medal, the most valuable player at state level, and selection in the All-Australian and TAC Cup Team of the Year sides.

[5] He featured in the under-16 Victorian basketball side[6] and was selected in the Australian under-17 squad alongside 2014 NBA number-five draft pick and Dallas Mavericks player, Dante Exum.

[11] He was named as one of the best players in the 92-point grand final victory against the Dandenong Stingrays, finishing with two goals and twenty-one disposals[12] and ended the season as the Eastern Ranges leading goalkicker[8] whilst also tying for second place in the best and fairest count.

[39] His dual position capabilities saw him draw comparisons to Richmond player, Dustin Martin, and Port Adelaide midfielder, Ollie Wines,[40][41][42] which led an AFL recruiter to rate him as a "star" and note that he has a "unique skill-set for an 18-year-old.

[49][50] He was predicted to play in the opening round of 2015 due to having an "AFL ready body";[51] however, his season ended abruptly after rupturing his ACL in his left knee at training in February.

"[69] In his fourth match, he recorded 21 disposals, 11 score involvements and seven tackles in the 63-point win against the Brisbane Lions at the Melbourne Cricket Ground,[70] which saw him rewarded with the round nine nomination for the Rising Star.

[71] The match drew high praise from the head of football writer at the Herald Sun, Mark Robinson,[72] while teammate, Jack Watts, labelled him an "absolute beast".

[73] After a handful of matches, Petracca became the favourite to win the Rising Star[74] and received praise from Australian Football Hall of Fame members, Matthew Lloyd and Wayne Carey, with the former claiming his ability would bring fans through the gates, and the latter compared him to Norm Smith Medallist and three-time premiership player, Steve Johnson.

[83] This focused change led many to believe that he would take his "game to the next level" for the 2017 season, including teammates, Dom Tyson[81] and Neville Jetta,[84] Fox Sports Australia journalists, Riley Beveridge[85] and Anna Harrington,[86] 300-gamer for Port Adelaide, Kane Cornes, who drew comparisons between Petracca and the reigning Brownlow Medallist, Patrick Dangerfield,[87] and former Melbourne player David Schwarz, who compared Petracca to the 2003 Brownlow Medallist, Mark Ricciuto.

Senior football writer with the Herald Sun, Jon Anderson, wrote in May that Petracca was an "extremely valuable commodity" and compared him to former players Tim Watson, Sam Kekovich and Ron Barassi, and claimed he could outweigh the two previous Brownlow Medallists, Nat Fyfe and Patrick Dangerfield, in his "natural affinity with scoring.

"[93] Another Herald Sun journalist, Sam Edmund, compared him to Dustin Martin and Robbie Gray and highlighted Petracca's self-confessed dreams of wanting to be remembered as one of the best players and a potential hall of fame member.

[2] During the thirty-eight point win against Essendon at Etihad Stadium in round six, Petracca recorded a career-high four goals[96] and was named in Melbourne's best players by AFL Media.

[97] He was named the best player on the ground for the annual Queen's Birthday clash in the four point win over Collingwood, in which he recorded eighteen disposals, seven marks and three goals and won the Neale Daniher Trophy after receiving eight out of a possible nine votes.