Carlton star Charlie Curnow could miss up to half of the 2020 season in a key blow for the club.

The 23-year old underwent knee surgery in November to repair a broken patella and was originally estimated to miss the start of the season.

However, the gun forward is still without a timetable, according to The Herald Sun.

Blues head of football Brad Lloyd told The Herald Sun Curnow is likely to return in the middle part of the season. 

“As we already communicated to our members and supporters last month, Charlie won’t be available for the start of the season,’’ Lloyd said on Monday night.

“This will likely mean a return to the field around the middle of the year.’’

Curnow had his 2019 campaign cut short after suffering ligament damage in Carlton's round 15 win over Fremantle and dislocated his patella playing a casual game of basketball in October.

The injury worsened when he slipped on tiles while walking up stairs in November requiring surgery.

Curnow averaged 12.3 disposals from his 11 games last season and booted 18 goals.