Sydney Swans delist unlucky injured defender Alex Johnson

The AFL future for injury-plagued Sydney defender Alex Johnson is unclear after the Swans made the difficult call to delist him.

Johnson had a torrid run with knee problems, undergoing five knee reconstructions before again rupturing his anterior cruciate ligament in August while playing only his second AFL match since 2012.

Facing another extended stint on the sideline, the Swans decided not to renew his contract for 2019.

They offered him a non-playing role for next season but Johnson, who played 47 senior games including their 2012 premiership, said he was still keen to play on.

Swans coach John Longmire praised Johnson for the impact he had in red and white.

"Alex has been an incredible servant of our club and has shown unbelievable resilience and he's a much-admired player among his teammates, coaches, staff and wider AFL community," Longmire said.

"This was an incredibly difficult decision to make but the reality is he faced another extended stint on the sideline.

"We explored the possibility of Alex staying involved with the club in a non-playing capacity, but he's keen to explore other opportunities."

Johnson said he was grateful for the opportunities and support from Sydney over the years.

"I would like to thank the club for the opportunities they have given me over the past eight years," Johnson said.

"Although it has been a very difficult last six years I will be forever grateful that they stuck by me and gave me every opportunity to get back and play at the highest level.

"While I am disappointed with the decision, my passion still remains to play football at the highest level."