By Miguel Rivera

Former two division world champion Sergio Martinez knows a thing or two about weight differences and catch-weights.

In Martinez's last fight, in June of 2014, fought Miguel Cotto at a catch-weight of 159-pounds. Cotto grabbed the WBC middleweight championship with a ninth round stoppage.

Martinez was suffering from numerous injuries as he entered that fight. His body never fully recovered and he retired the following year.

Saul 'Canelo' Alvarez (46-1-1, 32KOs) captured the WBC middleweight championship last November, at a catch-weight of 155-pounds, with a twelve round unanimous decision over Miguel Cotto.

Canelo makes the first defense of that title against Amir Khan (31-3, 19KOs) on May 7th at the T-Mobile Arena in Las Vegas.

Khan, who currently competes at welterweight, is moving up by eight pounds to a catch-weight of 155 for the bout.

Martinez competed at welterweight and eventually went to 154-pounds where he captured a world title and then several fights later he went to 160-pounds to win the middleweight crown.

He picks Canelo to win the fight and feels the weight difference will play role in the outcome. He sees Khan as a difficult opponent, but shares the opinion of several other fighters who are concerned about the weight difference in this match. Canelo puts on a lot of weight in the 24 hours that follow the official weigh-in, and he's usually over 170-pounds by the time he enters the ring. Canelo's last four fights took place at 155-pounds.

"It will be a fight that Canelo has to win. While Khan will not be an easy opponent, there is the issue of weight and this is going to complicate things, because on the day of the fight [Khan] will suffer [from the weight disadvantage]," Martinez told ESPN Deportes.