Quintana recently placed third on the podium at the Tour de France, however, he has noted an unknown illness that might have affected his efforts at the three-week race, citing possible allergies following stage 18.
He subsequently pulled himself from the Colombian team roster for the Olympic Games ahead of stage 21 on Sunday.
According to a press release from the Colombian Cycling Federation, Quintana will undergo further tests to determine his illness and the length of time he will need to recover.
President of the federation, Agustin Moreno Aristizabal and general manager, Jorge Ovidio Gonzalez, reported that Movistar doctor Jesus Hoyos Echavarria has given Quintana 20 days of needed recovery and that he will be tested to find out what the underlying health problems are.
The federation, along with the opinion of Dr. Hoyos Echavarria, announced Monday that Pantano will replace Quintana.
"This substitution was made at the discretion of national coach Carlos Jaramillo, relaying the alternate registration by the governing body of Colombian cycling to the Colombian Olympic Committee."
Pantano had a strong Tour de France; winning stage 15 to Culoz and placing twice second in stage 17 to Finhaut-Emosson and stage 20 to Morzine. He will meet his team requirements at races in Belgium and France before joining the Colombian team in Rio de Janeiro for the Olympic Games.