Richards, who originates from Birmingham, made only his second start of his career and he will never forget the occasion as he kept City's hopes alive.
Milan Baros had given Aston Villa a 72nd minute lead against the run of play and with only a minute remaining to be play City salvaged a last-ditch draw.
Joey Barton took a corner on the right and Richards, who is City's youth team captain, popped up to head home his vital equaliser to the delight of manager Stuart Peace.
Ominously for Villa their latest performances was produced in front of their lowest home attendance of the season, 23,847, which would have been even worse but for the 6,000 travelling City fans.
But the story could have been so much different if Darius Vassell had been in better form on his first return since his close season move from Villa to Manchester.
He should have had a storybook start but the England striker fluffed a great chance to give the Northern club an early lead. Jlloyd Samuel, who made a terrible mistake at Eastlands earlier in the season which led to Villa's 3-1 defeat, gifted his former colleague a clear run on goal with a poor pass-back.
Vassell, however, ran straight at Thomas Sorensen and the goalkeeper was able to make a brave save at the feet of the striker who a couple of minutes earlier had shot wide following a smart pass from Joey Barton.
Despite the absence of seven key players, City were often the more dangerous with Vassell's through runs proving troublesome for Villa's defence.
Villa survived another let-off from a close-range header by Antoine Sibierski, while Barton was only foiled from scoring with a low angled shot by another brilliant diving save from the inspired Sorensen.
Many Villa fans chose not to attend the televised tie and those who did were far from impressed with the performance of their favourites, who struggled to get to grips in midfield.
The frustration was often reflected in the way their attacks fizzled out against a City defence dominated by skipper Sylvain Distin.
Former Villa keeper David James had a relatively quiet first half as Villa's front men, Baros and Luke Moore, were often off the pace,
They were forced into an interval change when Wales international Mark Delaney, injured in only the second minute of the game, was unable to resume and was replaced by Liam Ridgewell.
In the high wind Villa were occasionally able to assert their attacking skill in the early part of the second half, but their finishing was almost non-existent and was reflected by the lack of response from their fans.
Finally, James was brought into action to block a James Milner shot following a Gavin McCann free-kick. Richard Dunne eventually cleared his lines in hasty fashion.
A spell of sustained City pressure produced some anxious moments and twice Gareth Barry had to come to Villa's rescue.
The most dangerous moment occurred in the 68th minute when teenager Richards headed Barton's corner goalwards only for Milner to chest the effort off the line.
Out of the blue Villa took the lead with their first clear cut chance of the match in the 72nd minute.
Baros bundled his way through and the ball ran loose into the path of Steven Davis, who calmly pushed his pass forward to the onrushing Baros to notch his ninth goal of the season.
But Richards was a youngster who would not be denied and unlike his previous effort cleared by Milner, he made no mistake with his last-minute face-saving equaliser.