Canelo Alvarez Picked Giant Sparring Partners to Replicate Callum Smith Height

Canelo Alvarez is 5'8". His opponent Callum Smith is 6'3".

BIG DIFFERENCE!

So, to prepare for their main event showdown at the Alamodome in San Antonio on Saturday night ... Canelo packed his training camp with super tall sparring partners!!

It's all captured on the DAZN docu-series "40 Days: Canelo vs. Smith" -- which chronicles both fighters as they get ready for the Dec. 19 event, which is available on the streaming platform in 200 countries and territories.

Fun Fact: soccer superstar Harry Kane teamed up with DAZN to executive produce the series.

Of course, Canelo is widely considered one of the top boxers on the planet -- he's 53-1-2 as a pro.

But, Smith ain't exactly a tomato can -- he's 27-0 and the reigning WBA super-middleweight champ. The fight will ultimately determine who is the #1 super middleweight in the world.

"He's one of the most difficult opponents I've faced," Canelo said on "40 Days."

"That’s why I'm training for a tall fighter like him, who’s intelligent, and also as strong as he is. I'm training for that."