Is it the chin or the heart that defines a fighter?
Amir Khan (31-3, 19 knockouts) accepted a big jump in weight to fight middleweight champion Canelo Alvarez — and he may answer that question in their HBO pay-per-view bout Saturday at T-Mobile Arena.
The Englishman Khan has been knocked out twice and sent to the canvas four other times during a career that has included a 140-pound junior-welterweight world title and his current standing as the World Boxing Council's No. 1 welterweight contender.
Khan is best known for his fast hands and boxing skills.
His unanimous-decision victory against heavy-hitting Marcos Maidana in 2010...