Against Iceland Messi had a second-half penalty saved and Argentina drew the game 1-1.
"We'll play with a knife between our teeth", he said.
Mandanda said he was yet to study Jorge Sampaoli's side, but he is wary of Messi.
"It's all great for the history books in Croatia but if we don't win against Denmark, when someone asks you what you did, what can you say?"
"After the first game [against Iceland] I gave you a good luck amulet that my wife gave me, I don't know if you threw it away or something", the reporter asked following Argentina's win over Nigeria.
Messi, 31, has come under fire for his performances in Russian Federation, where his classy opener against Nigeria helped Jorge Sampaoli's men into the last 16. Messi wore it all three games, they win the last one, and you can bet he'll be wearing it on Saturday against France in the round of 16.
The South Americans were overrun by Croatia, with Javier Mascherano and Enzo Perez chasing shadows in midfield as Croatia's Ivan Rakitic and captain Luka Modric ran the game in the middle of the park and ripped Argentina to shreds. "We were quite confident that we would be able to go through and fortunately that came through".
After that Messi left and Pantorotto turned towards the camera and said, "Ma, my dear, he put the string on his leg".
The reporter, according to a report from Barca Blaugranes, met Messi for the first time before Argentina's match against Iceland in Russian Federation.
While Nigeria's 19-year-old rookie, Francis Odinaka Uzoho is the youngest goalkeeper in the competition, Egypt's Essam El-Hadaryis the oldest player ever in World Cup history, at 45. But he also inspired his team off the pitch and showed a level of leadership unseen in previous matches, dragging his side through after a shocking group stage display. The 27-year-old Chelsea star has also contributed to three goals already in Russian Federation, and will be looking to add to that tally when the Red Devils go up against Japan in the round of 16.