By Mark Lamport-Stokes
Mexican Marquez stopped Diaz in the ninth round in Houston in February 2009 to claim the vacant WBA and WBO belts.
Diaz dominated the early rounds before Marquez turned the tide, swarming after his opponent in the eighth and ninth until the referee halted the contest.
"Our fight was the fight of the year in 2009 and it may be the fight of the year again in 2010," Marquez (50-5-1, 37 knockouts) told a news conference at the MGM Grand Hotel & Casino Saturday.
"A lot of people are asking me why Juan Diaz again? Number one, he is a great fighter and deserves a rematch. Number two, the people deserve a great fight like this."
Diaz (35-3, 17 KOs) viewed his sequel with Marquez as a chance for redemption.
"It's no secret my loss to Marquez is the one I want to get back the most," he said.
"I was dominating the first fight but I didn't finish (it off). This time that won't be the case."
The July rematch will take place at the Mandalay Bay Events Center.
(Editing by Tony Jimenez)