The 27-year old has failed to kick on since he was a key part of the Manchester City side that won the 2012 Premier League title with injuries being his main curse.
Richards, who spent last season on loan with Italian club Fiorentina, left the Etihad Stadium to join Villa on a free transfer recently and is now eager to reinvigorate himself at Villa Park.
Richards told City TV: "I didn't ever expect to do what I have done, but with my injuries I think I was hampered a lot. I think I could have achieved a lot more.
"I think my best years are ahead of me. It is sad to be leaving at this time.
"I do believe that, when I am 100 percent fit and firing, I am a very good player. My problem over the last couple of years has been picking up injuries and getting that consistency of playing."