Gennady Golovkin and Canelo Alvarez meet Saturday in a rematch for Golovkin's WBA and WBC world middleweight titles at T-Mobile Arena in Las Vegas.

After a controversial draw a year ago, what are the key areas and how do they compare ahead of the rematch?

Aggression: Golovkin

Gennady Golovkin, left, and Canelo Alvarez fought to a split draw one year ago. Ethan Miller/Getty Images

There is more animosity between the pair this time around, which hopefully makes for a more dramatic fight.

Canelo's two positive drug tests for the banned substance clenbuterol earlier this year -- which he claimed was due to contaminated meat -- has cranked up the bad feelings even more.

"It's definitely more personal, I don't like him," Canelo said.

"It will make me train harder and give it the extra push to knock him out on Sept. 15."

Also, Canelo (49-1-2, 34 KOs) cannot afford to be so reserved this time. Expect him to take more risks -- he will not want to face more criticism for a lack of aggression and ambition like he did a year ago. His machismo was hurt and is in need of repair.

But Golovkin (38-0-1, 34 KOs) is still likely to be the one marching down Canelo, stalking him relentlessly around the ring. The California-based Kazakh has been brooding over the decision and the failed drug test for the last year. Triple G was also annoyed about the rematch being pushed back from May 5.

"It's 100 percent different this time, different mentally, a different performance," Golovkin said.

"A lot of emotion. This is not only a boxing fight, not only a business fight, this is a true war," he said.

Golovkin did not seem disturbed by Alvarez's power punches last year and will feel he has a formula that has already worked against him. He will continue to walk down his challenger in the rematch, cutting off the ring and putting him under increasing pressure while looking for the openings to land his powerful blows.

Defense: Alvarez

Canelo Alvarez, left, did a good job avoiding Gennady Golovkin's jab in their first fight last year. Al Bello/Getty Images

Canelo had success early on avoiding Golovkin's jab, slipping punches and showing good foot movement.

The Mexican will have to show more of that throughout the rematch if he is to nullify Golovkin's jab and set up openings for himself on the counter.

Alvarez was also cute and elusive on the ropes against Golovkin, as well as moving away from danger by circling to his left. But Canelo's defense became leaky in the later rounds ... can he be more disciplined this time?

Tale of the Tape Golovkin Category Alvarez Kazakhstan Country Mexico 36 Age 28 38-0-1, 34 KOs Record 49-1-2, 34 KOs 5′10½″ Height 5'8" 70" Reach 70½" Orthodox Stance Orthodox

Golovkin might be content to take a few punches in order to land some of his own. GGG operates in the pocket, which means he is close enough to hit and be hit rather than dancing in and out of range. Golovkin is comfortable in the danger zone at close range, where he can unload his accurate shots with power.

But, with Golovkin within reach, it will also allow Canelo to land dangerous uppercuts.

Speed: Alvarez

Canelo Alvarez trimmed some muscle and seems to be in better shape for the rematch. Tom Hogan/Getty Images

Canelo's hand speed saw him land in flurries and right hands on the counter in the first fight. The trouble for Alvarez was that he could not do it regularly enough to control the fight.

Whatever your thoughts on the first fight -- and most people believed Golovkin should have got the decision -- Alvarez started the fight sharply, countering effectively and winning rounds.

If Canelo can land more of his quick combinations, allied to his fleet-footed movement around the ring, he will leave Golovkin trailing.

Canelo has posted pictures of his ripped physique on social media, leading some to question whether he has lost some muscle from a year ago and is lighter. If he is lighter, Canelo might even be quicker Saturday.

Work rate: Golovkin

Gennady Golovkin, right, threw 74 more power punches than Canelo Alvarez in their first fight. Al Bello/Getty Images

Golovkin might be 36 -- Canelo is eight years younger -- but it would be a surprise to see his conditioning fail him. He did not take a backward step a year ago and has the benefit of an interim fight and training camp (albeit brief: he dispatched Vanes Martirosyan in two rounds on May 5) over Canelo, who last fought a year ago.

Golovkin will aim to start quicker -- Canelo won some of the early rounds last time -- and perhaps put a bit more pressure on his challenger.

Alvarez will look back at the moments, like when he briefly wobbled Golovkin with a right hand at the start of Round 10, with encouragement. The quality was there from Canelo against Golovkin; there was just not enough quantity.

It was also Canelo who faded in the last fight over the last four rounds when he failed to sustain his early impressive movement.

Knockout ability: Draw

Canelo Alvarez, right, has the power an ability to potentially stop Gennady Golovkin. Al Bello/Getty Images

Canelo showed in glimpses he could catch Golovkin when he landed slick combinations in their first fight.

Alvarez is also capable of sickening knockouts, just like when he dispatched Amir Khan two years ago. Khan had started well, was quicker and moving around the ring confidently.

Golovkin registered 23 knockouts in a row until being taken to points by Daniel Jacobs in March 2017 but surprisingly failed to finish the job against Canelo when he had his rival trapped against the ropes on numerous occasions. Was it because Golovkin was concerned about being caught by a devastating right hand like the one Canelo pole-axed Khan with?

It might be Alvarez who is left looking for the knockout in the second half of the rematch, making him more likely to deliver a KO.

Golovkin needs to show a bit more imagination in creating openings, be bolder in his attacks, attack the body more, if he is settle the score by KO.

But what is more likely is that there is no knockout, since both unbeaten boxers have shown granite jaws until now.