Stuart Scott practices what he preaches ... especially when it comes to MMA ... so says the ESPN legend's sensei who tells us despite fighting cancer, the guy's a "battle horse" in the ring.
TMZ Sports spoke with Sensei Darin Reisler who was featured in a piece honoring Scott that ran during the ESPYs last night.
Reisler tells us ... the MMA footage was shot just 6 weeks ago -- in between cancer treatments.
"Stuart is a battle horse. The little bit that you saw last night – that was an hour and a half session ... grappling, ground fighting. He’s got a chemo port in his chest, is blind in one eye and gets kicked in the head and the chest ... the guy has NO quit in him."
Reisler says Scott has been coming to his Connecticut training center for the past 5 years -- and still wants to fight hard during every single session.
In fact, Reisler says Scott has said he doesn't want anyone taking it easy on him -- and once got a black eye during a sparring session. "The makeup department wasn't too thrilled."
As for receiving the Jimmy V award last night -- Sensei Reisler says, "It’s so great to see him getting recognized. But I’m very excited for the day that he won’t be fighting cancer – and the only fighting he’ll be doing is in the ring."