The former Mexican leader went on the record recently in an interview with CNBC, during which he touched on the Republican candidate and his views -- particularly regarding immigration.
Trump has made several controversial statements on the matter -- including a call for a temporary ban on Muslims entering the United States and a permanent wall at the Mexico border, which he said the Mexican government should also pay for.
"Mexican people, we are not going to pay any single cent for such a stupid wall," Calderon told CNBC Saturday. "It's going to be completely useless."
But the former Mexican president didn't stop there.
"The first loser of such a policy would be the United States," he continued. "If this guy (Trump) pretends that closing the borders to anywhere either for trade [or] for people is going to provide prosperity to the United States, he is completely crazy."
Since launching his White House bid, Trump has taken a firm stance against illegal immigration -- and last June stirred controversy with an assertion that the migrants crossing into the United States are largely the dregs of Mexico's jails.
"When Mexico sends its people, they're not sending their best," he said. "They're sending people that have lots of problems, and they're bringing those problems with us. They're bringing drugs. They're bringing crime. They're rapists."
Trump also said at the time that the United States has become a "dumping ground for everybody else's problems."
"It is incredible that a quite admirable society like the American society could produce such kind of candidates," he said. "I cannot understand that. No offense, no offense to America. So Donald Trump ... is ambitious but not exactly very well-informed man, I don't want to say ignorant, but he is not very well informed."
Calderon also noted that immigration from Mexico to the United States is in decline -- a decline that took hold while he was in office between 2006 and 2012.
"[Mexican citizens] don't want to go [to the U.S.]. They can work for a motor company not in Detroit, I am sorry to say," he said. "They are working for a motor company in Hermosillo and Toluca, so Mazda is coming to Mexico, Honda is coming to Mexico. Those kids have jobs in that industry in Mexico."
Trump has not yet responded to Calderon's remarks, although he did keep up his fiery rhetoric over the weekend on Twitter, one of his preferred methods of communication.
"The New Hampshire drug epidemic must stop. If elected POTUS- I will create borders & the drugs will stop pouring in," he tweeted Saturday.
Trump also took multiple swipes at fellow GOP contender Jeb Bush.
"Everybody is laughing at Jeb Bush-spent $100 million and is at bottom of pack. A pathetic figure!" he wrote.
Himself a former pro football executive -- he owned the New Jersey Generals of the short-lived United States Football League between 1983 and 1986 -- Trump also offered his early assessment of Super Bowl 50 between the Denver Broncos and Carolina Panthers.
"So far the Super Bowl is very boring - not nearly as exciting as politics - MAKE AMERICA GREAT AGAIN!" he tweeted during the first half.
"Jeb Bush has zero communication skills so he spent a fortune of special interest money on a Super Bowl ad. He is a weak candidate!"
The USFL folded in 1986 after an attempt to compete directly with the NFL failed.
It appears, though, that the NFL championship game wasn't boring to everyone. CBS' coverage notched the third-highest rating in American television history -- an average of 112 million viewers -- trailing only the previous two Super Bowls, which averaged 114 million and 112 million, respectively.