"I think multiple people could beat her. Hillary Clinton is not unbeatable," Rubio told conservative radio host Hugh Hewitt on Friday.
When Hewitt asked the Florida Republican if he feared squaring off with the former secretary of state on foreign policy, Rubio was quick to criticize Clinton's record.
"I would ask her the question I would ask her now, 'You were the secretary of state during the first four years of the Obama administration. Name one significant foreign policy achievement, now or after you left,'" Rubio responded.
"The reset with Russia has been a disaster, the Middle East is more unstable today than it's been in I don't know when -- and that's saying a lot -- our relationships in Latin America and democracy has deteriorated in Latin America, the Chinese are increasingly aggressive, our partners around the world view us as less reliable," he added.
Rubio's made no secret of the fact that he's been mulling whether or not to launch a presidential bid in 2016. Clinton, the presumed Democratic contender, has also not yet made a decision either way.