The former Dally M five-eighth of the year has turned down a deal to extend his stay in the nation's capital, where he has been since 2015 since coming from Sydney, where he previously played for Penrith and the Wests Tigers.

The Raiders believe the 27-year-old will join forwards Junior Paulo and Shannon Boyd in exiting the club at the end of the year.

"Blake had an offer on the table last year and he rejected that offer, and as in the game you've got to move on and unfortunately he didn't take the offer and we've moved on, basically," Raiders recruitment boss Peter Mulholland told ABC radio.

"We've got some (space) in the salary cap, but not the amount that Blake would be requiring to stay at this stage.

"Things can change. He's obviously been looking around for a period of time and if circumstances change within our cap over the next month or two then there may be an option there.

"It's unfortunate, but that's the way it works with the salary cap. Everybody can't keep everybody, it's just a fact of life."

Austin formed a successful partnership in the halves when Aidan Sezer joined Canberra in 2016 as the Raiders made it to the preliminary final.

Ealier this year he was dropped to second grade, but Austin has responded with some good form as the Raiders look to end the season on a high.

Australian Associated Press