Sylvester Stallone Says Torn Pec Injury Forced 'Rocky II' Plot Twist

Sylvester Stallone came within a hair's breadth of tanking "Rocky II" because of a gruesome injury, and you won't believe how he powered through to shoot the flick!

Sly and Arnold Schwarzenegger sat down with Harvey, and for the first time ever together they talked about their unbelievable rivalry and how it blossomed into a close friendship.

View this post on Instagram Arnold's trainer and compadre, bodybuilding legend Franco Columbu, trained Sly for "Rocky II," and when Franco challenged Sly to a bench press competition, the actor was game ... until he ripped his pec off the bone.

Sylvester Stallone Through the YearsHere's the problem. The injury occurred a month-and-a-half before Sly was…