As reported by Spanish outlet Marca, Simeone was talking to reporters as part of the buildup for Los Rojiblancos'pre-season clash with Paris Saint-Germain on Monday.
However, the press conference was dominated by Simeone's comments on Ronaldo and Messi, two players widely regarded as the greatest ever to grace the sport, which came to light during the World Cup this summer.
A 'leaked voice message' revealed the Argentina boss as saying: "I would choose Messi surely, without any doubt."
In an attempt to clarify the comments in his press conference, Simeone told reporters: "Yes, I said it, but the explanation was to Germán talking about football as a conversation between friends, not talking about who is the best in the world.
"But saying that for a normal club, with normal players, Ronaldo would surely fit better. But Messi, surrounded by great players, is still the best in the world."
Both Ronaldo and Messi endured underwhelming World Cups this summer, with Ronaldo scoring four goals in Portugal's opening two matches but failing to help his country get any further than the last 16 stage.
Meanwhile, Messi suffered from a combination of poor form and an inability to make an impact on matches as a result of Jorge Sampaoli's poor tactics as Argentina exited the competition at the same stage, showing only a few flashes of brilliance such as his electric goal against Nigeria in La Albiceleste's final group game.