MARK Baguley's season is in jeopardy after the Essendon defender underwent knee surgery this week.

The small backman has been carrying the problem for several weeks but the club has decided to put its vice-captain in for an operation.

The Bombers are unable to put a timeframe on Baguley's return but are hopeful he will be back in the red and black by the end of the year. 

"We'll wait for the surgeon's advice after he catches up with Mark after the surgery settles and we'll get a better idea from there," said Justin Crow, the Bombers' fitness boss. 

"It's entirely possible (that he will return to the team). Mark will be really keen to do that. We'll take the surgeon's advice and do the best thing by his long-term playing career." 

It is a blow for the Bombers ahead of their Friday night meeting with Hawthorn, particularly as Essendon has relied on Baguley to shut down the competition's small forwards in recent years.

The 29-year-old has been a constant member of Essendon's defence the past three seasons. He was elevated to the leadership group at the end of last season and then to the vice-captaincy following the WADA bans to 12 senior players at the club in January.

Under coach John Worsfold Baguley has also spent time in the forward line this year where his ferocious tackling pressure has been important.

Crow said Baguley had done well to keep playing while dealing with the problem.

"Over the last few weeks he has had swelling in his knee after games," Crow told the club website.

"This is from an old injury that he has in the cartilage in his knee and it has gradually been getting worse and worse."