Josh Gross has the story at SI.com:
A championship battle of undefeated light heavyweights is slated to headline UFC 98, SI.com has confirmed. Rashad Evans (13-0-1) will defend his UFC belt May 23 against Lyoto Machida (14-0).
Evans-Machida is the third planned main event for the MGM Grand Garden Arena-hosted card in Las Vegas. UFC heavyweight titleholders Frank Mir and Brock Lesnar were originally scheduled to make the title whole, but Mir bowed out late last week after injuring his knee while training.
The UFC quickly scrapped the anticipated rematch in favor of Evans' first fight since he stopped Forrest Griffin to take the 205-pound title last December. Following his decision win Saturday over Keith Jardine, former UFC champion Quinton “Rampage” Jackson was offered the first crack at Evans. Though he was left off Ohio's list of medically suspended fighters stemming from the March 7 card in Columbus, a short turnaround for what would have been Jackson's third fight in five months is believed to be his justification for declining the fight.