Charlie Dean was set to start a full-time internship on Monday but Collingwood's recruiting team had other plans.

The 20-year-old was overlooked in last year's draft and became a top mature-age prospect this season, winning the prestigious Fothergill-Round-Mitchell Medal.

Named in the VFL's Team of the Year after averaging 15.1 disposals and 7.3 marks in his nine matches, Dean showed he is composed under pressure with elite intercept marking ability and an impressive work rate.

The Williamstown defender was selected with pick 2 in the 2021 AFL rookie draft last Friday.

"(Being overlooked) taught me a lot about how to stomach disappointment and use it as fire," Chaz said.

"To finally hear my name called was a big relief and to know I was joining a big club like Collingwood and staying in Melbourne was a relief too.

"There was just so much joy and overwhelming happiness - I'm stoked to be here."

Chaz predominantly played up forward for Sandringham in the 2019 NAB League but his coach at Williamstown, Justin Plapp, switched him to the other end of the ground this year and it proved an inspired move.

"I really like Sam Collins, he's a competitive beast and really strong defensively and I also like Jordan Ripley because he has a lot of skills for a key back," Dean said, when asked about players he hopes to emulate.

"I'm most looking forward to working with Jordan Roughead and Darcy Moore, I can't wait to be a fly on the wall and learn from them.

"There is a great bunch of players at the club and it will be a huge task to overtake anyone in the senior side but that's the goal.

"Hopefully playing on big bodies in the VFL will hold me in good stead."