ESSENDON's mystery man Nigel Lockyer has returned to train at the Bombers as he trials to win the final spot on the club's' list with the Dons also testing out another hopeful.

AFL.com.au revealed in December that Lockyer was in Essendon's sights as it looks to fill the final open spot on its list.

The Bombers were coy about their interest in Lockyer when he was first spotted at their Tullamarine base, but he has rejoined the club this week in a bid to impress Essendon scouts.

The club has a place open which it can fill through the Pre-Season Supplemental Selection Period (SSP), or leave it open for the mid-season draft this year.

They have an open place due to recruit Lachie Johnson's knee injury.

The Bombers have also flown over Nathan Ireland from Western Australia to test for a place on the list.

Ireland, who will turn 20 next month, is a 198cm key defender who played with Swan Districts' reserves and league side throughout 2019.

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He is considered a later developer who is mobile and athletic for a player his size.

Lockyer travelled to Victoria last month and was set to train, however an ankle injury prevented him from joining the Bombers group.

But AFL.com.au understands he is back this week and was training with the Bombers on Thursday. They returned to training in Melbourne this week after spending last week training in Coffs Harbour.

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Lockyer, 22, is a 190cm forward who has an eye-catching leap and can play in attack and defence.

Nigel Lockyer (left) at Essendon training on Thursday. Picture: essendonfc.com.au

He has worked hard to improve his fitness in recent months and will partake in training with the Bombers in a bid to be added to their list.

Lockyer, who has represented the Northern Territory in basketball, tested at the NAB AFL State Draft Combine last October, and has played at the NT Thunder.

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He joined the Thunder via the Rovers in the Central Australian Football League.

The Bombers are one of up to eight clubs who could add a player before the season starts through the SSP, with Carlton opening up a place by moving first-round draft pick Brodie Kemp to the long-term injury list.

Adelaide, Collingwood, Hawthorn, West Coast and potentially Richmond, pending their next move with the retired Alex Rance, can all fill one place, while Melbourne has left two places open.