The popstar's boyfriend broke it all down on "The Rich Eisen Show" on Tuesday -- just days after his quarterback, Patrick Mahomes, said Swift has been working on some X's and O's on the whiteboard.

Kelce revealed his boo takes everything she does seriously -- and that includes her football fandom -- so she is, indeed, learning how to move chess pieces around the gridiron.

So far, Kelce says nothing's made its way into Andy Reid's playbook just yet ... although watch the clip, it certainly seems the tight end thinks it could happen one day.

Of course, if it ever goes from Taylor's mind onto Reid's call sheet -- Kelce said it'll almost certainly be a snap designed to get him the rock.

"She's a little biased," Kelce said with a laugh, "and just creates plays for me. So, we'll see if they can make it to coach Reid's office."

Kansas City's season officially begins in just two days against Baltimore ... so it's probably unlikely we'll see a Swift creation against the Ravens.