Collingwood have invited retired Australian beach volleyballer Max Guehrer to train at Olympic park over pre-season, with the 26-year-old potentially in line for an AFL list spot.

The Supplemental Selection Period opened on Monday, with the Western Bulldogs announcing the opening signing of the window with the acquisition of delisted Demons speedster Oskar Baker.

Fremantle have confirmed a pair of trainees for the summer ahead, while the Tigers, Bombers and Saints are also said to have handed train and trial deals to AFL hopefuls.

Collingwood are reportedly the latest club to open their training regimen to an outside name, with Guehrer, who stands at 204cm tall, joining Craig McRae's program this week.

Guehrer retired from beach volleyball in late October after winning a bronze medal with Australia in the Asian Beach Volleyball Championships and was a member of Australia's Asian Continental Cup title-winning side last year.

The mature-aged prospect has since begun working at his partner's winery in Kuitpo, South Australia, but recently landed in Victoria to explore his chances of a football career.

With the departure of Brodie Grundy to Melbourne this off-season, Collingwood's ruckman pecking order has decreased, with Guehrer a chance to join the queue.

Darcy Cameron is set to retain first-string ruck duties in 2023, while veteran ruck-forward Mason Cox is seen as a best 22 figure at the Magpies.

Depth option Aiden Begg made his debut in 2022, but was limited to just the three appearances due to form and injury.

Collingwood would be able to sign Guehrer as a Category B Rookie for 2023, while forward-midfielder Tom Wilson extended his place as a Category B Rookie for next season following an exemption from the AFL.

The SSP is scheduled to run until February 15.