PADDY McCartin has announced his retirement from AFL football after his run of concussion issues.

The Sydney defender, who has been sidelined since April due to his most recent concussion in round four this year, is understood to have informed teammates of his decision on Monday.

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The 27-year-old, who was the No.1 pick at the 2014 AFL Draft when he joined St Kilda, had been going through a process on his playing future as he had further assessments with medical experts and brain specialists.

After being delisted by the Saints at the end of 2019 after 35 games with the club due to the effects of his concussions, McCartin was determined to make it back to the top level, a feat he achieved last season.

Paddy McCartin and the Swans celebrate their win over Fremantle in round 18, 2022. Picture: AFL Photos

He played at VFL level with Sydney before being selected as a rookie at the end of 2021, returning to the AFL with the Swans last season.

He played 24 games for the club last year, including the Grand Final when the Swans were beaten by Geelong, and formed a formidable defensive partnership with his youngest brother Tom.

Tom and Paddy McCartin at Sydney training on May 11, 2023. Picture: Phil Hillyard

The pair became intercept stars for the Swans, with the oldest McCartin showing his superior marking abilities and kicking strength for a key position player.

The former Geelong Falcon played the first four games of this season before going down early in the Swans' clash with Port Adelaide at the SCG with a head knock.

He finishes his career with 63 AFL games.

"I am obviously disappointed that I'm no longer able to continue to do what I love, but I have to be guided by the specialists and I know that this is the right decision for me," McCartin said.

Paddy McCartin in action during round four, 2022. Picture: AFL Photos

"I want to thank the Sydney Swans for the faith shown in me and the opportunity to pursue my dream of playing AFL football. It has been a privilege to play for this great club and I will remember this time fondly.

"I want to especially thank Lucy, my family, teammates, coaches and medical staff for their wonderful support through this challenging period – I’m very grateful."

McCartin's retirement comes two weeks after Hawthorn ruckman Max Lynch also announced his retirement due to concussion issues.