8:47 AM PT -- Sources connected to Karrueche tell us ... Memphis recognized Karrueche while hanging out at a club and asked for a photo.
We're told the whole exchange was friendly ... but they're definitely NOT dating.
Tran was hanging out in Miami with Memphis Depay -- a Dutch soccer superstar who plays for Manchester United.
In fact, the 21-year-old phenom just signed a reported $40 MILLION contract with Man U back in May -- so, dude's got money.
So far, no word if Karrueche and Memphis are friends ... more than friends ... or nothing at all.
But if there is something there ... upgrade?