A late header from Christian Benteke, who has replaced Bent as the number one striker, moved Villa out of the Barclays Premier League relegation zone.
Lambert said: "Darren was in the squad, it was the same on Saturday. I just picked the same group. I do what think is best for Aston Villa.
"But honestly, I don't have a problem with Darren Bent and I do rate him as a player.
"I've no problem with his attitude in training, none whatsoever.
"Did he storm off? No, not a thing. I would tell you. I thought he was fine. I read the team out. The most important thing is Aston Villa.
"Will I listen to offers in January? Honestly my main concern is winning games for this club, nothing else."