Bent, who spent last season on loan at Fulham, is Villa's record signing, having arrived from Sunderland in January 2011 in a deal worth a reported £24 million.
However, the former England striker has fallen out of favour under Lambert and will spend the next month with Championship side Brighton and Hove Albion.
He said: "Darren wanted to go out on loan about a month ago but with Christian Benteke being suspended we had to keep him here.
"It gets Darren's career going again and that's why I loaned him to Fulham last year, to try to get him going. But Darren wanted to go himself as well.
"Christian is coming back after Saturday and I think Gabby Agbonlahor and Andi Weimann will find their feet again in terms of goalscoring."
"We just play a different way," added the manager. "Darren came to me a month ago saying he wanted the chance to play more games (and go on loan), which I agreed to do," he said.
