IT was a fight Amir Khan acknowledged would be the toughest test of his career and it ultimately proved a challenge too far against Saul ‘Canelo’ Alvarez.

The Bolton star was knocked out in the sixth round by the reigning WBC middleweight champion in Las Vegas after making the better start in the opening exchanges.

But Alvarez is not regarded as one of the world’s best boxers for nothing and showed his power to weather Khan’s early storm and dish out a devastating right hook that ended proceedings at the new T-Mobile Arena in the fight capital of the world.

It left Khan flat out and deflated but once the dust settles, the 29-year-old can take pride in the fact he had the gumption to take the fight on against a man only beaten once in his career – by Floyd Mayweather Jnr on points three years ago.

Going into the fight, Khan was banking on his speed being his main threat – a fact not lost on Alvarez either, whose camp had talked up the Boltonian’s chances in the final days before the showdown.

It was that speed of hands that was a standout feature of the opening rounds.

Khan started brightly despite the big rise in weight to the 155lbs level and two good quick combinations set the tone early on.

Since joining Virgil Hunter’s stable in San Francisco, Khan has become more tactically astute and that showed again as he took his opportunities for quick combinations before withdrawing and avoiding leaving himself open.

Canelo, in contrast, started cagily and while he landed some body shots, it was clear the Mexican was keen to weigh up the threat Khan posed as the challenger won the first round and continued in the same vein.

Alvarez was on the front foot and commanding the centre of the ring but Khan silenced a noisy crowd of support behind the favourite.

The former Olympian was more than a match for Alvarez, though as time wore on the champion started to push forward more with good jabs and left-handers.

He showed more intent and had his best round to date in the fifth when he cut Khan above the right eye with a big jab.

It was a sign of the damage Alvarez could cause and with just 23 seconds remaining of the sixth round, he caught Khan sweetly with a big right hand that sent the British fighter crashing to the canvas.

It was such a huge hit that referee Kenny Bayliss did not even bother to finish a count and there was some concern from Alvarez how badly hurt his opponent was.

Thankfully following medical attention, he was okay and back on his feet.

It was a fourth defeat of Khan’s professional career but contrasting with the previous three. This time, he will not have to try and rebuild his reputation – it remains intact after a good showing against a bigger and more experienced champion.

Khan spoke afterwards about having the guts to take on the Alvarez challenge and few could argue.

A return to welterweight is expected and Khan still has much to be positive about despite losing his biggest payday to date.

Whether it is an all-British showdown against Kell Brook or a rematch against one of those earlier conquerors Danny Garcia – this experience will stand the Bolton superstar in good stead.

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Round-by-round snapshot

Round One: Khan starts brightly with two good combinations as Alvarez starts cagily but lands a good body shot. Khan is brightest. ROUND TO KHAN.

Round Two: Alvarez is more on the front foot but Khan still lands with good combinations. Alvarez gets in a good left but Khan is the busier man. ROUND TO KHAN.

Round Three: Fast hands again from Khan see him land shots but Alvarez is unmoved and lands jabs of his own. LEVEL ROUND.

Round Four: Khan continues to use his speed and Alvarez misses some big shots. ROUND TO KHAN.

Round Five: The champion starts to find his form and lands some good shots. A big jab cuts Khan above his right eye. ROUND TO ALVAREZ.

Round Six: Alvarez is finding his range now and while Khan still gets in some good combinations, body shots and left-handers from the champion land well. Then the right hook knocks Khan to the canvas and it is over. ROUND TO ALVAREZ.