The extent of his injury was revealed by an MRI he had Saturday in South Florida, which also showed he had a minor strain to his upper right calf. He hurt himself running out a grounder for Team Venezuela in the sixth inning of Wednesday's loss to Team USA in the World Baseball Classic.
Asked by reporters Sunday if the injury might sideline Prado for the first month of the season, Marlins manager Don Mattingly said "not necessarily" and said "I'm just not putting a timetable on it."
Despite the news that he won't be ready for Opening Day, Prado said he was relieved that he doesn't have a more serious injury.
"I was worried, yeah. I didn't know what it was. I didn't know exactly what was going on with my leg," he told reporters. "After I talked to the doctor, I was just concerned and disappointed that I let my teammates down. I let the Marlins down because I was not able to come back here healthy."
Prado, who signed a three-year, $40 million contract extension in the offseason, said his concern now is getting the injury "fixed and not worry about feeling this injury during the regular season."
A career .293 hitter over 10 major league seasons, Prado hit .305 and drove in 75 runs for the Marlins last season.
With Prado out, the Marlins are expected to turn to either Miguel Rojas or Derek Dietrich to play third base. Both of the players were already expected to make Miami's 25-man roster out of camp. Rojas played 16 games at the spot last season but only started once. Dietrich started seven games there in 2016, part of his 13 appearances at third.
Prado, 33, played in left field for Venezuela on the night he suffered his injury. He said Sunday that he doesn't believe playing out of his normal position was a factor in his injury and also said he doesn't regret playing in the WBC.
"It was fun. It was intense. It's hard to believe that this time of the year how intense those games can get," Prado told reporters. "It's a short competition, so every game matters. I think that's one of the reasons why you've got to get locked in mentally and prepare yourself for every out and every at-bat."
Information from The Associated Press was used in this report.