McDonald, Newnes, and rookie Luke Parks were all informed this week that they won't be handed new AFL contracts.
Newnes notched 155 games across eight seasons at St Kilda before moving to Carlton at the end of 2019 as a delisted free agent.
The 29-year-old added a further 52 games across three seasons at the Blues to take his career tally to 207.
His career highlight came in round 12, 2020, when he kicked a 45m after-the-siren match-winner against Fremantle from outside the boundary line.
McDonald tallied 81 games across five seasons at Melbourne, but he was only able to add a further five games since his move to Carlton at the end of 2020.
Parks notched just eight games across two seasons at the Blues.
"Jack is a testament to what hard work can earn you in AFL football, to play 200 games to this point at the highest level is a terrific achievement that Jack and his family should be incredibly proud of," Carlton's head of list management Nick Austin said in a statement.
"Oscar is also a terrific character who brought a lot to our group. While he was unlucky with his injuries, the resilience he showed to continue to persevere and maintain a positive presence around the club was impressive.
"Luke had his share of bad luck through injury this year. However, his perseverance to come through state level to earn two years in the AFL system proves his strong work ethic."
The Blues missed out on a spot in the finals after losing their last four games of the season, including a one-point loss to Collingwood in the final round.
18°C