Five things we learned from Canelo Alvarez-Amir Khan

— -- LAS VEGAS -- Canelo Alvarez made the first defense of his middleweight championship with a one-punch knockout of Amir Khan in the sixth round on Saturday night.

Alvarez (47-1-1, 33 KOs) now has 15 days to decide whether he will face unified titlist Gennady Golovkin (35-0, 32 KOs), the No. 1 contender to his WBC title, or be stripped of his belt.

Here are five things we learned from a wild night at the brand-new T-Mobile Arena.

1. Alvarez is as ready for GGG as he'll ever be

Alvarez will be the first to tell you he's not a middleweight despite, you know, being the 160-pound champion of the world. But after five straight fights at his preferred catchweight of 155 pounds, it's time for him to make the full leap to 160. No more games.

Alvarez has done well to showcase his maturation into a calculated, dangerous counterpuncher. He showed poise against Khan's hand speed and has vastly improved as a body puncher. He might not be the destroyer his gruesome knockouts of Khan (a blown-up welterweight) and James Kirkland (an equally overaggressive junior middleweight) might suggest, but he has enough pop to handle himself at the higher weight.

Would Alvarez be considered the underdog against Golovkin if they fought later this year? Without question. But closing in on the 50th fight of his career despite being just 25, Alvarez is at the peak of his powers. He's either going to defeat GGG or he won't, but choosing to further delay the biggest fight boxing can make in 2016 would be a disservice to the sport.

Golovkin, and boxing fans in general, have waited long enough.

2. A defiant, nasty Canelo is a fun Canelo

With apologies to his lone English catchphrase, "I was born ready," the Mexican star doesn't really say much or offer any emotion. So witnessing his quasi-heel turn Saturday, when he motioned for Golovkin, who was sitting ringside, to enter the ring, was refreshing.

Alvarez broke character by saying, "We don't f--- around," and that he's not scared of anyone. He went on to call out the segment of hard-core Mexican fight fans who won't give him his due. And in response to hearing that Golovkin trainer Abel Sanchez told media members that Alvarez didn't have "the balls" to face GGG, he pulled no punches by saying, "He can come and touch them if he wants and he'll surprise himself."

This ain't your mama's Canelo Alvarez, and in a sport dependent upon the marketing of bravado and trash-talk to sell itself, that's not a bad thing.

3. Alvarez still has room to grow as a star

Recent retirements by Floyd Mayweather and Manny Pacquiao allowed Alvarez the chance to stake his claim as boxing's biggest star. His push was helped by a sponsorship deal with Tecate, which saw Alvarez featured in a series of television ads during fight week (including strategic placement during commercial breaks on SportsCenter).

Alvarez is already halfway to crossover stardom, thanks to his looks and growing highlight reel of knockouts (with the stoppage of Khan as spectacular as it gets on the elite level). But along with consistently showing a feistier and colorful side to his personality, committing to learning English will help him better connect with casual sports fans in the United States.

He will also need to be a man of his word. Alvarez's postfight comments regarding his interest in fighting Golovkin floated between encouraging and noncommittal. In one breath he said he's willing to fight Golovkin, today, at 160 pounds. But moments later, he said he doesn't care about the WBC's 15-day mandate to make the fight or even fighting for the belts in general.

Boxing is already filled with enough politics and filibusters. Alvarez can set himself apart by walking the walk.

4. Boxing needs more like Khan

Despite just three fights as a full-fledged welterweight, Khan's lust for a superfight saw him boldly move up eight pounds to challenge for Alvarez's middleweight title at a catchweight.

We can say what we want about Khan's suspect chin or the fact that his dare-to-be-great narrative isn't without holes (let's not forget, he sidestepped a number of big fights in his own division for two years while courting Mayweather). But there's an old-school quality to the risk Khan took Saturday and the fearless style he employed.

Khan (31-4, 19 KOs) was willing to put it all on the line in search of glory and a career-high purse, despite the inherent danger he faced. It's a strategy that isn't for everyone. But it makes for entertaining fights and high drama, which Khan's career has produced consistently due to his equal mix of vulnerability and sublime offensive talent.

In his postfight interview, Khan challenged Alvarez, saying, "I think it's time for Canelo to step up to GGG, just like I stepped up to him." If more top fighters shared Khan's ambition, boxing's popularity rating would be in a much different place.

5. Khan's window is closing

It would be irresponsible not to acknowledge the downside to fearless matchmaking, and how the accrued damage can shorten careers. While Khan, 29, still has plenty of business waiting for him at 147 pounds, it was unsettling to see him knocked cold in such vicious fashion, with his head bouncing off the canvas.

As Khan tweeted himself after the fight, "That's boxing for you," and he's right. Anything can happen when two pugilists step between the ropes. But Khan's poor punch resistance and even deeper issues avoiding counter right hands simply aren't going away. His defensive flaws appear to be ingrained.

Knockouts can come in many different varieties, of course. But Khan has now been stopped in devastating fashion three times and was wobbled and hurt in a handful of other fights, particularly against opponents not known for their power.

These are signs that don't bode well for his long-term future, as the next knockout loss could be one too many, with calls for Khan to walk away with his health intact likely to follow. He's not there yet and will likely have his choice of a number of attractive fights in boxing's glamour division moving forward. But at the very least, there's a feeling that Khan is much closer to the end than the beginning.