Rival clubs are reportedly expressing interest in acquiring the services of a contracted key defender, joining a group of backmen rumoured to potentially be on the move this year.

St Kilda's Dougal Howard has reportedly found himself in movement discussions around the league, according to the Herald Sun on Wednesday.

The 27-year-old Howard is contracted at Moorabbin for a further season, meaning any such switch for the key stopper would have to come via a trade agreement.

The Saint has already been subject to a trade once in his AFL career, swapping Port Adelaide for St Kilda at the end of the 2019 season.

According to the Herald Sun's report, Howard is currently being paid in the realm of $600,000 per season at St Kilda, with the Saints understood to be weighing up significant list moves as the off-season edges closer.

Howard has been a consistent feature in the Saints' backline since swapping Alberton for Moorabbin, playing 75 games in St Kilda colours since crossing state lines.

St Kilda was also reported to be interested in swooping on Carlton's Tom De Koning prior to the ruck-forward's recommittal at Princes Park, suggesting the club is seriously exploring the possibility of bringing another key-position player to the Saints.

Among the other key defenders reportedly receiving rival overtures this year are West Coast's Tom Barrass, Geelong's Esava Ratugolea, and Adelaide's Tom Doedee.

Barrass remains contracted at the Eagles, Ratugolea finds himself without a deal beyond 2023, while Doedee holds a restricted-free-agent status this year.

The Saints, though, have one of their own reportedly being eyed off, with forward-midfielder Jade Gresham having been linked to a move to the Blues. The nifty utility is a restricted free agent at the conclusion of this season, having yet to re-sign.

Irrespective of what plays out this October, this year's exchange window is poised to be a busy one for a bevy of clubs and players.