BIG3 co-founder Jeff Kwatinetz is NOT throwing in the towel on Kobe Bryant playing in his league next season -- telling TMZ Sports he trusts his source.
After Kobe's rep shot down Jeff's previous claim that he'd be suiting up for the 2019 season, we saw JK out in NYC ... and he made it clear he's not backing down.
"There's no mix-up. Someone who's a good source, who I'm not gonna reveal, says he's gonna play."
Jeff acknowledges Kobe's been telling people it's not true -- but Kwatinetz doesn't believe it's a hard pass .