Johnson was ruled ineligible by Miami late last week after an investigation revealed that members of his family accepted "impermissible travel benefits" from a member of the school's former coaching staff. The university said Johnson was not aware of the benefits, personally accepted nothing and that his family had been told they were allowed.
Multiple sources told ESPN.com's Andy Katz that Johnson was suspended because former Miami assistant Jorge Fernandez used his personal frequent flyer miles to pay for a plane ticket used by Johnson's mother. According to the sources, the violation was discovered because the receipt came back to Fernandez's University of Miami email account.
Fernandez is currently an assistant coach on Marshall's staff.
The NCAA told Miami that Johnson "must repay the value of benefits that were unknowingly received from a member of the former coaching staff" and sit out one game. Johnson satisfied the second of those requirements by missing Miami's win over No. 22 Florida State on Sunday night.
It's a major boost for the Hurricanes (17-10, 8-6 Atlantic Coast Conference), who are fighting to reach the NCAA tournament.
Johnson is averaging 10.6 points and 6.9 rebounds this season for Miami.
The entire NCAA process related to Johnson's eligibility took a bit less than a week, and the speedy resolution was something Miami desperately wanted.
The NCAA and Miami have worked together in a joint investigation of the Hurricanes' compliance practices since last year, that inquiry largely revolving around the claims former booster Nevin Shapiro -- now a convicted Ponzi scheme architect serving a 20-year sentence in federal prison for masterminding a $930 million scam -- made in an article published by Yahoo! Sports.
The NCAA found the links to Johnson's family, and Miami coach Jim Larranaga was told on Wednesday that college sports' governing body wanted to speak with Johnson. The NCAA and Johnson talked Thursday, and he was declared ineligible on Friday.
Declaring an athlete ineligible is typically the responsibility of the school when a violation is believed to have occurred. The school then presents its case to the NCAA and asks for reinstatement. The Hurricanes hoped the NCAA would have decided by Sunday, but when no word arrived, Johnson could not play in that game against the rival Seminoles.
It's not known which coach is alleged to have arranged the benefits, or what they were. Johnson has not been made available for comment.
Larranaga said in an interview aired Monday on SiriusXM radio that "one of the former assistant coaches evidently did violate a rule" regarding the impermissible benefits. During his weekly appearance on the Big 12 Conference coaches' call, Missouri coach Frank Haith -- the former coach at Miami -- said he has cooperated with the NCAA throughout its investigation.
"I'll just be glad when this thing is over with," Haith said Monday.
Haith also had high praise for Johnson on that same call, without specifically discussing any details on the extra benefits that someone from his staff allegedly provided.
"Reggie is a wonderful young man. ... I feel bad for him and his family," Haith said. "I know he'll get through it, though."
The NCAA moved quickly, per Miami's request. And now the Hurricanes will have to move quickly as well -- Johnson was not allowed to fly with the team for its game at North Carolina State, so alternate arrangements to get their 6-foot-10 center there were quickly being made.
Information from The Associated Press contributed to this report.