Flahavan picked up the set-back in a collision in the final pre-season friendly against Bristol City and is expected to be out for six months.
The 33-year-old missed the first two games of the season, but returned to Paul Groves’ squad last month before discovering the full extent of the injury.
“My main aim now is to get myself fit and strong. If I could be involved at the end of the season, it would be a bonus, but I’m probably looking at trying to come back stronger for next season,” he told afcb.co.uk.
“I’ve just got to keep my head right, not let it get on top of me and focus on my rehab.
“I remember coming off after the Bristol City game and speaking to the gaffer and I said there wasn’t something quite right, but I didn’t realise it was bad as it was.
“I had a couple of weeks out and then started doing some light work for a couple of weeks, and, again, it wasn’t right. When we got the scan results back it was bad news and it looks like I’m going to be out for a long time.
“I was trying to be optimistic and say I could get back in three or four months’ time, but I’ve got to be realistic and if I try and push it, it could tear again, which would set me back even more. I’ve got to manage it right.
“I wanted to thank the supporters for their well wishes and messages. They’ve been great.”
Flahavan’s absence meant that Chad Collins was named amongst the substitutes for the Cherries’ two home fixtures earlier this week.
Collins is expected to continue to keep his place in the squad this Saturday, while Benjamin Buchel waits for international clearance.
“They’re both young lads and it will be a good experience for them to be involved in the squad,” he said. “They need to push Shwan (Jalal) to keep him sharp, and they’ve got a role to play.”