Coach Mike White canceled postgame interviews to join Johnson at Tallahassee Memorial as his players boarded a bus for the two-hour trip back to Gainesville. According to the school, White will remain with Johnson at the hospital overnight.
Johnson's parents were flying in from Virginia to be with their son.
"Please keep praying for @Keyontae and his family. We all love him," White posted on Twitter.
Please keep praying for @Keyontae and his family. We all love him.— Mike White (@MikeWhiteUF) December 12, 2020
The Gators were coming out of a timeout Saturday when Johnson collapsed on the court. He was given emergency medical attention and taken to the locker room.
Like most of his teammates, Johnson tested positive for COVID-19 during the summer. Although the cause of Johnson's ailment was not immediately known, the coronavirus can lead to myocarditis, a viral infection of the heart muscle.
Before the incident, Johnson had just finished an alley-oop on a pass from Tyree Appleby. He celebrated with teammates and walked toward the sideline; as the team broke its huddle, he collapsed on the court and players screamed toward the sideline for help.
Several Gators were in tears and a couple buried their faces in towels as White gathered his team to say a prayer.
Officials gave the teams time to regroup, and the game continued a few minutes later. Florida State coach Leonard Hamilton said administrators twice gave the Gators the option of stopping or continuing the game -- at that time and again at halftime -- and said they ultimately decided to play. White let his players make the call.
"Whatever they thought was in the best interest of their team, then I would accept it,'' Hamilton said. "My administration asked me, and I told them we would be OK with whatever they decided. It was my understanding that they wanted to play.''
The Gators weren't the same afterward, as both teams seemed rattled. Florida (3-1) was ahead 11-3 after Johnson's dunk, but the 20th-ranked Seminoles (3-0) scored the next seven points and went on to an 83-71 victory.
Hamilton, who did not see Johnson fall, said some of his players were crying, and he questioned whether they would be able to be effective in the game. The longtime Florida State coach said some players were on their knees praying during the timeout shortly after Johnson had collapsed.
"Those types of things can affect you in some adverse ways,'' Hamilton said. "We're just all hopeful and praying that he's OK. If it affected our players in an emotional way, I can imagine what the situation was with his teammates.''
Johnson, a junior forward from Norfolk, Virginia, is averaging 19.7 points per game this season and is considered an NBA prospect. He scored five points in four minutes Saturday.
Johnson is known for his versatility and floor leadership and is considered a leading candidate for SEC Player of the Year. He averaged 14 points on 54% shooting from the floor and 7.1 rebounds as a sophomore.
The Associated Press contributed to this report.