Kate Upton Took Cornholing Way Too Seriously ... Injures Foot

Kate Upton's gotta turn down the intensity when it comes to cornhole -- somehow she injured herself playing a sport so laid back, most people do it with a drink in their hands.

We got the supermodel at LAX, just a couple days after she posted a pic of her swollen and bruised right foot ... and she was still feeling the pain.

Watch as Kate explains how in the world she got hurt in the first place, and why the injury's forcing her to do one of the most UN-supermodel things.

The good news for Justin Verlander -- her face and bod still look pristine.