Jones-Buchanan made his debut in 1999 and has since played over 400 games for the Rhinos.
The veteran has not been named in Thursday's 19-man squad to face St Helens but fellow back-rower Stevie Ward is included.
Ward will return for the first time in six months and Agar says Jones-Buchanan will get a chance eventually despite not playing since May.
He told the Yorkshire Evening Post: 'Jonesy will get some footy before the end of the year. He is training really well.' Leeds have four more games to go before the end of the season and Agar has demanded a strong finish as his team look to move away from the relegation zone.
'It is a competitive league with a lot at stake at the moment and we are coming up against some good teams,' Agar added.
'Some of the holes in us footy-wise will take time to iron out but I do think we have made plenty of progress in that. 'Defensively our effort has been great, we have kept teams to two tries, no tries, one try - but I think we will gain plenty of confidence from our attack by putting a couple of 40 points on. That will do us a world of good.'