This is the kind of content Giants fans needed -- here's video of Saquon Barkley training like a mad man just 6 months after his ACL surgery ... and the NFL star looks GREAT!!!

The 24-year-old running back suffered the devastating, season-ending injury to his right knee in a Week 2 matchup against the Bears last September ... which Barkley referred to as "probably the weakest moment of my life."