MELBOURNE youngster Alex Neal-Bullen has dislocated his knee for the second time in just over a month but the Demons are hopeful the 18-year-old will only be sidelined for up to three weeks.

The Demons sent Neal-Bullen, pick No.40 in last year's NAB AFL Draft, for scans after his right knee gave way during a training drill on Monday.

Neal-Bullen was carted from Gosch's Paddock in obvious discomfort following the incident.

No structural damage showed up in the scans.

Demons football manager Josh Mahoney told the injury was a "minor dislocation".

"Alex had an incident at the end of training yesterday where he dislocated his patella," Mahoney said.

"It's the same knee that he dislocated pre-Christmas in a wrestling session.

"This is only a minor dislocation and we'd expect him to recover quite quickly."

As reported by in mid-December, Neal-Bullen suffered a similar injury during a training drill.

Mahoney said the club was investigating why Neal-Bullen had suffered the same injury two times in a short space of time.

Mahoney said the Demons were hopeful Neal-Bullen would be available for selection in the NAB Challenge series, beginning for Melbourne on March 5 against Fremantle, following his rehabilitation.

The Demons are set to explore other methods in regard to Neal-Bullen's training program after the recurrence.

"There's a few things we'll have to add to his program to prevent this from happening again," Mahoney said.

After his initial injury, Neal-Bullen rejoined his teammates at training after the Christmas break and attended the club's camp at Maroochydore on Queensland's Sunshine Coast over the past fortnight.

The Glenelg product was regarded as a likely top-30 pick leading into the national draft and Melbourne was pleased to land Neal-Bullen alongside childhood friend Billy Stretch, who was taken at pick No.42 as a father-son recruit.

Melbourne still views Neal-Bullen as a potential debutant in 2015.