By Edward Chaykovsky

Ronnie Shields, who trains WBA/IBO junior middleweight champion Erislandy Lara and IBF junior middleweight champion Jermall Charlo, is not exactly sure why WBO junior middleweight champion Saul 'Canelo' Alvarez is heading up to a catch-weight of 164.5-pounds to fight Julio Cesar Chavez Jr.

The two Mexican star finalized their agreement for an HBO Pay-Per-View battle on May 6th.

The reason Shields is stumped is because last year the biggest fight in boxing, arguably, between Canelo and middleweight king Gennady Golovkin - fell apart due to weight. For much of the year, the two sides were haggling over the weight. Canelo wanted the fight to take place at 155, and Golovkin was unwilling to drop down any lower than 160.

For much of the last two years, Lara has been calling for a fight with both Golovkin and Canelo.

As far as Canelo-Golovkin, Shields has no idea why that fight hasn't been made. The two sides are still discussing the contest - and it may take place in September during Mexican Independence Day weekend.

His theory, which is shared by a few others, is Canelo and his handlers are waiting for Golovkin to get a little older. Golovkin is 34-years-old, while Canelo is only 26.

"He’s going to fight Chavez Jr. at 165lbs but he won’t fight Golovkin at 160lbs. What sense does all of this make? I don’t think Canelo is afraid of Golovkin, but if you call yourself a middleweight champion — which is the title that you won but never defended at that weight, then why fight for it? It just doesn’t make sense to me," Shields told On The Ropes Boxing Radio.

"If the fight does happen. I think everybody is going to be happy because they want to see two of the best fighters in the world fight each other. Take nothing away from Canelo, he is one of the best fighters out there and is one of the most well known fighters out there also. It just seems like they have a hard time making this fight and I don’t know why. Maybe they think that ‘GGG’ is going to get older and that he will have a better chance that way. I don’t understand it but I think everybody in the sport is really looking forward to that fight."