The Mexican tells Boxing Scene that Mayweather is a 'protected' fighter when he fights in Vegas.
"I know both of those fighters, and it is difficult to be able to beat Floyd Mayweather, and even more so because he is a protected fighter in Las Vegas," Marquez said.
Mayweather's last 12 fights have been in Las Vegas. November 2005 was the last time he fought outside Vegas when he defeated Sharmba Mitchell at the Rose Garden in Portland.
Marquez has fought both fighters before, facing Pacquiao four times and losing to Mayweather in 2009.
"It is very difficult to penetrate the guard of Mayweather.
"But with the speed that Pacquiao has, he can do it," he added.