The England international, who is Villa's record signing after joining for an initial £18m from Sunderland in January 2011, has been benched for the recent matches against West Bromwich Albion and former club Tottenham Hotspur.
However, the Scot has stressed that Bent's omissions were simple selection decisions rather than a result of any animosity with the player.
"I've never had a problem with Darren. I have a laugh and a joke with him," said Lambert.
"Of course, I understand people get frustrated when they are left out. You'd be more worried if they weren't. But he has not been knocking on my door. There was never a problem."
Bent is in contention for a recall when Villa travel to Fulham this weekend.