As the runner-up for the 2015 Heisman Trophy, the Stanford Cardinal's Christian McCaffrey has already proved he's a star on the gridiron.

The junior running back is more than just a great football player, however. He's also a musician.

Last year, we found out in a College GameDay feature that McCaffrey can play the piano. That apparently just set the stage for his latest (musical) highlight video.

On Thursday, Stanford Athletics posted footage of McCaffrey covering Billy Joel's "Piano Man." No, not on the piano—on the harmonica. While he has a bright future in football, the 20-year-old Cardinal star also has what it takes to be a successful musician.

[Stanford Athletics]