Gennady Golovkin and Canelo Alvarez
Gennady Golovkin remains the favorite over Canelo Alvarez. Pictured: Golovkin throws a punch at Canelo during their WBC, WBA and IBF middleweight championship bout at T-Mobile Arena in Las Vegas, Nevada, Sept. 16, 2017. Ethan Miller/Getty Images

Gennady Golovkin is the early betting favorite for his middleweight title rematch with Canelo Alvarez, but his odds have interestingly changed from their previously proposed May bout.

Golovkin (38-0-1) finally agreed to a deal that he felt was fair as his rematch with Canelo (49-1-2) was confirmed earlier this week to take place at the T-Mobile Arena in Las Vegas on Sept. 15.

The duo served up a boxing classic in their first meeting in September last year but despite many feeling "GGG" had done enough to come away with the victory, the judges controversially scored the contest a split-decision draw.

The rematch was slated to take place on May 5 but it was called off in April as Canelo was suspended for six months by the Nevada State Athletic Commission following his failed drug tests in February.

Las Vegas bookmaker Bovada gave Golovkin -170 bettings odds for the May rematch as his performance in the first fight clearly played a role in him remaining a favorite over the Mexican who had +140 betting odds.

However, he is a slightly bigger favorite for the rematch now taking place in September as Bovada has given him -190 betting odds while Canelo now has +155 betting odds.

A major theme during the negotiations for the first rematch, particularly from Canelo's camp, was how, as the younger fighter by eight years and having had the experience of going 12 rounds with the unbeaten Golovkin, he would emerge as the winner in a potential sequel.

However, oddsmakers clearly disagree, likely for two reasons. Golovkin fought Vanes Martirosyan as a short-notice replacement for Canelo last month, meaning he will be more active than his counterpart who will have gone a year without fighting when they clash.

The second reason is likely the failed drug tests — Canelo and his promoters, Golden Boy were adamant that his failed drug tests, for the banned substance clenbuterol, were a result of consuming contaminated meat in Mexico.

But many in the boxing world, Golovkin's camp included, do not buy it and with the likelihood of Canelo being extra careful this time, he will be fighting clean in September — meaning if he did cheat in the first fight and arguably lost, his chances don't look any better for oddsmakers.

Regardless, Golovkin's promoter Tom Loeffler believes the rematch will be even bigger, thanks to the various storylines now involved.

"It’s a much bigger fight with all the controversy that has gone on and no love lost between the guys," Loeffler said. "In the first fight, it was a respectful promotion, but in the second fight, with the positive test and the way Gennady had to scramble to be able to fight on May 5, he is very edgy. Canelo is very edgy, so I think that’s going to get things heated up."

The first fight notably generated 1.3 million pay-per-view buys and was the third-biggest gate in boxing history with $27 million.