How important is quality sparring?

[Master]

Ali said he practiced his defence technique sparring and having Holmes sparring with him to get in condition must have helped against Foreman.

[JazMerkin]

The Maccarinelli/Afolabi fight is a perfect example. People wrote Ola off as a tomato-can before he got in the ring, ignoring that he has sparred with the Klitschko's, James Toney & Tomasz Adamek. This makes someone a better fighter, pretty much all the best fighters in the post-war era have had themselves quality sparring partners. I do think Warren is acknowledgin this though, as he has been trying to get DeGale in with the likes of Mayweather & Jermain Taylor