Why was Antonio Gates lighting into Philip Rivers on Chargers sideline?

Anyone able to read lips?

Watch above as San Diego Chargers tight end Antonio Gates appears to rip into his long-time quarterback, Philip Rivers, and say something somewhat threatening. We think we have a good idea of what he's saying including Gates threatening to beat a certain body part of Rivers.

But why?

This shouting match came after the Chargers settled for a long field goal at the start of the second quarter. Rivers scrambled on third-and-7 the play prior, so we're guessing he might have missed an open Gates on the play.

The Chargers eventually lost in a wipeout to the Kansas City Chiefs, 33-3.

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This is not the Gates we know. Of course, this hasn't been the easiest season for him — he began the season with a four-game suspension and the Chargers are sitting at 2-8, tied for the fewest wins in the NFL. The Chargers' frustration cup hath runneth over this seaosn.

Here's a theory on why Gates might be barking at his quarterback from the past 12 seasons, having reached old-married-couple status by this point: CHECK OUT HIS NEW 'STACHE.

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Eric Edholm is a writer for Shutdown Corner on Yahoo Sports. Have a tip? Email him at edholm@yahoo-inc.com or follow him on Twitter! Follow @Eric_Edholm