Essendon will be without ruckman Tom Bellchambers for at least the first month of the season after the club decided his injured ankle would require surgery.
The 24-year-old sustained the injury during a match simulation session last week and was expected to only a month of pre-season training.
However, consultation with a specialist this week revealed the injury was worse than first thought, and would require surgery and a three-month stint of the sidelines - meaning Bellchambers will miss all of the NAB Challenge series and at least the club's first four matches.
The injury is set to stress the Bombers' ruck stocks, although coach Mark Thompson is confident the team will be able to manage the situation until his return.
"To lose a player of Tom's ability for that amount of time is not ideal, but we have to look at the positives and Tommy is a resilient character," Thompson told the club's website.
"He'll have the full support of the fitness and medical team to help him get back out playing as soon as possible," he said.
"We have a number of quality players that can play in the ruck including Paddy Ryder and Joe Daniher, and we picked up Fraser Thurlow in the rookie draft over the summer."