You know that rivalry week is here when someone's diag gets spray painted.

According to MLive, in the wee hours of Sunday morning, some Michigan State University fans took it upon themselves to vandalize University of Michigan's diag. The U of M diag, which bears the signature Michigan block "M", was gone over in green spray paint, with a green "SU" added to the end, changing it to "MSU".

Typically, fans and/or fraternity's take up the vigil of protecting the diag at either school, which is what "members of UM's Theta Xi fraternity" were trying to do when they got there Sunday night, but they were already too late. The last time U of M's diag got tagged was in 2014. MSU's Sparty statue has been vandalized as well, getting painted "maize and blue in both 2015 and 2013".

While this may be the start of rivalry week, the end of rivalry week will come this Saturday when the two teams go head-to-head. Read more about diag getting vandalized and see the picture here.