Richards used a fake blood capsule to ensure wing Tom Williams could be replaced by Nick Evans during the Heineken Cup quarter-final defeat to eventual winners Leinster at the Stoop 32 months ago.
The ex-England No8, who toured twice with the Lions in 1989 and 1993, resigned from his post with Quins in August 2009 having taken over at the club four years earlier.
"I want to get back into the game," Richards told the Sun.
"It's been a bit of a blip in my career but we all make mistakes. What's important is to learn from them."
"I still have ambitions to win more major trophies."
Richards coached Leicester to back-to-back Heineken Cup crowns in 2001 and 2002, as well as four successive English Premiership titles.
He left Welford Road in 2004 after 23 years as a player and coach with the Tigers, initially joining French side Grenoble before guiding Harlequins back to English Rugby's top-flight following their relegation from the Premiership.