Lockhart, now 23, had been playing for Melbourne's VFL affiliate the Casey Demons in 2018.

The midfielder fills the Demons' final spot for their 2019 roster, as they prepare for the beginning of the home and away season next week.

Melbourne Demons' general manager of football operations Josh Mahoney said this was the first year of the AFL's new supplementary selection period.

Through this new system, teams were allowed until March 15 to add players to their rookie list.

"By passing on our last pick in the rookie draft we had a spot available and today we have added Jay Lockhart to our rookie list for the season," Mahoney said.

Lockhart's season with the Casey Demons proved strong with his effective kicking, a key advantage he'll bring to Melbourne.

He even managed to notch 10 goals during his stint in the VFL.

Lockhart's had numerous strong performances with the Casey Demons including their match against the Northern Blues in August 2018 where he netted two goals, 10 effective kicks and 10 effective handballs.

"Jay had a terrific season at the Casey Demons last year and was unlucky not to get drafted at the time," Mahoney said.

"To Jay's credit he took the disappointment of not getting drafted to fuel a really strong pre-season at Casey Demons.

"He came back in terrific condition and we are really happy that we have been able to reward his attitude with this spot."

Lockhart will add depth to the Demon's midfield which was one of the team's priorities after their disappointing final performance against the West Coast Eagles.

Mahoney added that when the Demons were weighing up how they would best make use of their final roster spot for 2019, Lockhart ticked all the boxes.

"When we were considering how to use this position on our list, it made sense to add a player who knew our system and had played under our coaches," Mahoney said.

"Jay was a perfect candidate and we are sure he will make the most of this opportunity."

Before Casey, Lockhart was the Lefroy medalist during his best-on-ground performance with Tasmania in their loss to the NEAFL team.

He also played with the Northern Launceston Bombers during which he was a key contributor in the two premiership-winning seasons he played with them.

The Melbourne Demons' will look to get off to a strong start against the Port Adelaide Power for their season-opener on March 23 at the MCG.