Leicester City, desperate for a win to take them off the foot of the Premiership table, had begun at a gallop with Muzzy Izzet forcing Keller into a brilliant one handed save inside two minutes.
Thereafter the Foxes continued to dominate, peppering the Spurs goal from all angles.
On 37 minutes Paul Dickov raced onto an Alan Rogers pass, outstripping Mauricio Taricco for pace, but Keller had spotted the danger and sprinted from his line to smother the ball at the feet of the Scottish international.
But the American keeper went from hero to zero in the space of a single minute when his embarrassing gaffe handed his former club the lead.
Les Ferdinand headed a long punt from Ian Walker into the path of Dickov whose eight-yard shot was not exactly full of venom.
Keller should have dealt it with comfortably but instead he held his head in shame after he fumbled the ball and allowed it to slip between his legs and over the line.
It was the first goal Spurs had conceded since Pleat became caretaker manager and prompted the home fans into ironic choruses of 'USA!'City continued to press after the break. James Scowcroft flashed a header just wide and then they squandered a great chance to put the game beyond Spurs on 76 minutes when from a quick breakaway Marcus Bent fired straight at Keller.
It was to prove a costly mistake as Spurs fashioned a breakaway of their own which ended in a sensational equaliser on 79 minutes.
Substitute Mbulelo Mabizela - making his first appearance for Spurs - had been on the pitch for just four minutes when he dispatched a fantastic rising shot from 22 yards into the top right hand corner of Walker's net.
The visitors then completed an unlikely win in the final minute when Stephane Dalmat crashed an angled shot against an upright and Kanoute pounced to ram the rebound home from eight yards.
The game ended on a sour note with Kanoute stretchered off after a lunge from the frustrated Izzet who was fortunate to escape with a yellow card.