UFC 173: Barao vs. Dillashaw: UFC 173: Barão vs. Dillashaw was a mixed martial arts event held at the MGM Grand Garden Arena in Las Vegas, Nevada on May 24, 2014. A Bantamweight Championship bout between Renan Barão and Raphael Assunção was targeted as the event headliner. However, Assunção opted to decline the bout as a rib injury sustained in his last bout at UFC 170 had not healed enough to resume the proper training in advance of the event. Barão instead fought T.J. Dillashaw in the main event.