The defender's effort from the edge of the box denied the determined visitors a win, and once again demonstrated the never-say-die attitude of the players coming so soon after Karim Rossi's late winner against Nantwich Town on Monday.
Academy manager Dave Wright readily admitted that this match was a fitness exercise for the squad, and the warm conditions were certainly testing for both sides at Stone Dominoes' ground.
He decided to offer a chance for some fringe players to impress, with changes that included Lucas Dawson, George Rigg and Andy Musungu being rested ahead of Saturday's concluding friendly against Newcastle Town.
Peter Makrillos was one of a few to make the step-up from the Under 18s, while Manny Parry returned to central defence to partner Ben Heneghan. Rossi's efforts on Monday night were enough to earn him a starting berth too alongside Callum Pilkington up front.
Kick-off was delayed by a quarter of an hour after Brentford's late arrival, and their lack of a warm-up showed. Stoke did most of the pressing early on although City 'keeper Dan Bachmann was forced into a smart stop after a corner was flicked on at the near post.
On 24 minutes, Brentford should have gone ahead after a melee in the six-yard box resulted in one of their forwards having a clear shot at goal from two yards. However, somehow he managed to clear the bar, much to the relief of the City back four who believed there had been a foul in the build-up.
Karim Rossi had the young Potters' first real chance on the half hour - his 20-yard drive stung the hands of the visiting 'keeper after the impressive Wato Desire had won possession in midfield.
Stoke were generally on top for the rest of the half, yet found it difficult to break down a hard-working and organised Brentford defensive unit.
Three changes were made by Wright at the break, including the introduction of Matt Sandiford between the sticks.
Brentford gained the upper hand as the heat began to tell on both sides, and they almost went ahead on 61 minutes. James Campbell's overhit backpass put Sandiford into trouble, but the onrushing forward couldn't make the most of the opportunity.
A few moments later they did take the lead, however, when a mix-up between Makrillos and Sandiford left the Brentford striker with a chance that he simply couldn't miss.
Wide men Jadan Hall and Marcel Barrington were trying in earnest to make something happen for Stoke, but things weren't going their way in the final third and they must have felt it wasn't to be their day when Sam Westley was denied a penalty after being felled in the area.
However, as the referee was checking his watch for full-time, Richardson's corner found Keane lurking on the edge of the area. The central defender did well to bring the ball under control, before firing into the bottom left corner with the aid of a deflection.
Wright said afterwards: "It was scrappy game, and testing for our lads against such hard-working opposition.
"We can take plenty from it though as it gave some of the others a chance to get their match fitness up."
City's Under 18s were also in action at the venue, and they strolled to a 4-1 win against Brentford thanks to a brace from Derice Richards, plus a goal apiece for Kieran Monlouis and Kris Scott.
Stoke City: Bachmann (Sandiford 45); Westley, Parry, Heneghan (Keane 45), Campbell; Hall, Desire (Glasgow 85), Makrillos (Richardson 75), Nardiello (Barrington 45); Rossi (Thomas 72), Pilkington.