Bent was sidelined for the final three months of last season with a ligament injury suffered against Wigan in February which also ended his hopes of being part of England's Euro 2012 squad. He is currently struggling with the injury again but, after seeing a specialist on Wednesday, Lambert believes rehab work should help rather than another operation.
Lambert said: "Darren had a scan on Wednesday on the ankle that he hurt and there's still little things in there that need to be cleared up. I think that's the problem. It's from the last injury but he doesn't need surgery now."
He added: "I don't know how long he will be out but it's about the healing....rehab really. It's not floating bone, and he is getting there, but there's still a wee bit to go. It's a blow because we need any goalscorer and strikers."
Prior to his latest injury Bent had already lost his place to £7million summer signing Christian Benteke, who has quickly become a favourite with the Villa fans.
Lambert said: "I think Christian has built up a good relationship with them because of the way he plays and the way the big guy's been.
"I think at every club you go to there's always somebody the fans really like. For somebody as young as he is, once it sinks it what he's doing, I think he'll be a really big player."
Villa have now half a dozen players on the injury list but Lambert is still looking forward with relish to games against Manchester United, Manchester City and Arsenal in the next fortnight.
He said: "The injuries are mounting but that's the game of football, you have to trust the ones that go out for you. We've got Manchester United and we'll go to try and win it. The players will relish the next three games.
"Nobody's expecting us to do it, but we've earned the right to play them and we'll go and try and win."