MELBOURNE young gun Christian Petracca has learnt a "harsh lesson" after breaking his toe playing basketball during the Christmas break.

Petracca, who had been in the midst of a strong pre-season, has suffered a small crack to the little toe on his right foot. 

The former No.2 draft pick will be forced off his legs for the next month while he recovers, before he builds his fitness back up to a point where can resume full training.

Petracca, who was the early favourite for this year's NAB AFL Rising Star award, didn't play a game in his debut year at Melbourne after rupturing his ACL last pre-season.

The Demons expect Petracca will be able to continue strength conditioning on his knee despite the injury.

Disappointed Melbourne coach Paul Roos hoped the setback served as a lesson in professionalism for the talented 20-year-old midfielder.

"Christian’s rehab up until this point has been going really well, but when you’re an AFL player, you need to understand that everything you do impacts your ability to prepare and contribute to the team and this incident is clearly an interruption," Roos said.   

"We have been very clear as a club about not putting expectations on our first year players, so it's important to keep some perspective about this.

"It’s a harsh lesson for Christian, but one we are sure he is going to learn from as he develops as an AFL player."