Khan dominated the opening stages of the fight but then Garcia turned the encounter on its head with a brutal left hand counter near the end of the third round that sent Khan into a dizzying nightmare.
Despite staggering around like a drunk after taking an eight count, Khan survived and came out for the fourth but was immediately in trouble again and was afforded a standing count by referee Kenny Bayless when he looked on the brink of dropping again which helped clear the fog somewhat.
However, his boxing smarts had deserted him at this stage, and near the end of a slugfest of a round, Garcia put Khan down again with a left-right combination. The Bolton fighter got up again, but this time the referee waved it off to hand Garcia a sensational win.
With the victory, unbeaten Garcia defended his WBC title and also took Khan’s WBA title and the vacant Ring Magazine belt.
Despite going into the fight with an unbeaten record, Garcia started as a big 5/1 underdog and in the opening two rounds there was no indication that he would be able to cope with Khan’s speed.
The British fighter was moving in and out with lightning quick combinations and Garcia’s sluggish responses suggested Khan could have an easy night as long as he boxed smart.
Garcia was bloody around the eye after just two rounds, and his father and trainer was not talking in the corner with that same cocky confidence that had so annoyed Khan in the build-up.
However, Garcia has always been known as a counter-puncher and it was a sweet-as-a-nut left near the end of the third round, landed when Khan got too ambitious, that turned everything on its head.
Khan went in for another combination but this time he walked onto a whipping left from Garcia that could easily have ended the fight there and then as Khan dropped to the canvas.
Khan got up and with just 14 seconds left in the round decided to carry on but he looked to be residing on another planet before the bell saved him.
The minute’s rest had a minimal effect as Garcia raced out of the blocks and took advantage of Khan’s disorientation with some more brutal blows.
A right from Garcia saw Khan stagger away from him, and it initially looked like the referee stepped in to stop the fight but instead he gave Khan a standing count.
The round continued for two more compelling minutes, and Khan actually landed some shots on pure instinct, but in a brawl, the street-ready Garcia was always going to hold the aces, and in the end it was a cumulative effect that finally finished Khan off, with the right that sent him to the ground almost incidental although Garcia did follow it up with a more powerful left on the way down.
Again Khan got up, but this time the referee was not going to let the fight continue as he waved it off.
It was a sensational performance from Garcia who moves to 24-0 with the win and who silenced the doubters who questioned his ability and résumé going into the fight. Superstardom and big money fights await him after such a high profile annihilation.
However, Khan's second successive defeat leaves his career in limbo; he now looks a tough sell in America and his dream of stepping up to fight Floyd Mayweather at welterweight looks like fanciful, pie-in-the-sky stuff now.
This was a devastating defeat for him, in more ways than one. It is likely he will need to return to Britain to try and rebuild his career, but even in his homeland it looks like being a long road-back to prominence for the Bolton man.