The announcement comes less than a week after Davis submitted Wagner Prado in the second round at UFC 153 in Rio de Janeiro. Davis' win came nearly 10 months after he suffered his first professional loss -- a unanimous decision to Rashad Evans on Jan. 28.
Davis (10-1) replaces Chael Sonnen, who was removed from the bout after accepting an offer earlier this week to coach on next season's version of "The Ultimate Fighter."
Sonnen will coach opposite current 205-pound champion Jon Jones. The two are expected to fight in April 2013.
Griffin (19-7) will seek his second win in a row. He defeated Tito Ortiz by unanimous decision at UFC 148 in July.
Dos Santos lifted the heavyweight belt from Velasquez on Nov. 12, 2011, by knocking him out in the first round.