Naomi Osaka is VERY close to being off the market ... 'cause the #1 ranked womens tennis player in the world is getting REAL close with rapper YBN Cordae!!!
In fact, Cordae made a recent cameo on Naomi's IG -- leading many to think the appearance was their public coming out party.
But sources close to the two tell TMZ Sports ... while they're spending a lot of time together lately -- and they like each other -- they're not "officially" an item. At least not yet.
As one source put it, "Just give it a week.