On September 8, the UFC announced via twitter that top Lightweight contenders Nate Diaz and Gray Maynard would be meeting for a rubber match at the TUF 18 Finale on November 30. Diaz immediately responded via Twitter that he'd prefer to be facing champion Anthony Pettis next.
Now he's tweeting again:
@ufc Cant make it november 30th ive gotta high school reuinion i have to tend too...
— Nathan Diaz (@NateDiaz209) September 23, 2013
Presumably Diaz is having some fun at the UFC's expense but time will tell.
Also it should be noted that Diaz and Maynard fought first on The Ultimate Fighter season 5 tournament in a non-sanctioned contest that doesn't appear on their official records. Diaz submitted Maynard in that bout.
Their second bout occurred in January, 2010 and Maynard took home a split decision win.