S.I. Swimsuit Model Nina Agdal -- Watch My Ass Shoot a Basketball

Sports Illustrated bikini model Nina Agdal got game ... even in her PJs.

Nina threw on some butt-cheek revealing short shorts and hit the hardwood recently for one of the hottest shoot-around sessions we've ever seen.

Selflessly, she posted the footage to Instagram along with the caption, "Who needs active wear. Bball in tha pjs."

Fun Fact -- Nina is a HUGE basketball fan who actually played a little bit in her home country of Denmark. Now, she's a big Miami Heat fan.

So, the big question ... who ya got in a 1-on-1? Nina ... or Matt Stafford's super-hot sharp-shooting fiance Kelly Hall?