Bentley, who was hurt in a tackle by Sam Kasiano which earned the Dragons prop a spell in the sin bin, will see a specialist next week, according to his coach.
“It is not a real good one,” Wolf said. “James has got some ligament damage around his spine. He could not finish the game and was in quite severe pain.
“James is really disappointed. He has more appointments with specialists next week and we are obviously hoping on the positive side there.
“We are hoping for the best but there is a chance and likelihood that this could be an extended period.
“He is a good player – and you always miss your good players. For whatever period he is out for we will miss him.”
Bentley missed St Helens’ Challenge Cup final win over Castleford in July with a broken leg and will be absent against Leeds on Friday in the penultimate round of the regular season.
Speaking when the move was announced back in June, Bentley said: “I am looking forward to joining the Rhinos for next season. I am a Leeds lad and grew up supporting the team, sitting on the South Stand wall and dreaming of running out on the pitch as a Leeds player.
“I have had a taste of success at St Helens and I want to make sure I come to Leeds and play my part in helping the team win even more silverware in the years ahead.
“I have had four really enjoyable years at Saints and made some great mates for life. I am doing everything possible to get back healthy and on the pitch as soon as possible and hopefully I can finish the year on the best possible note with St Helens.”