The France centre back has been Messi's team mate for two years and he will cross the forward's pass when Les Bleus take on Argentina in a mouth-watering second round tie on Saturday.
Umtiti, who is expected to start at the Kazan Arena after being rested in France's last group game against Denmark, said: "I see him everyday. It is very hard to stop him. He's got outstanding qualities.
"We will try to stop him but he's not the only one in this Argentina team, they have other strikers."
But while Messi can rely on a reliable Luis Suarez at Barca, he is a bit more on his own with Argentina, with Gonzalo Higuain having notably not scored in his last eight outings with the national team.
He also has to deal with the weight of a whole nation expecting him to win the World Cup in what is likely to be his last shot at the biggest trophy in football.
"He is different with Argentina than with Barcelona," said Umtiti.
"He does not have the same players with him and their way of playing is different but he has saved them on several occasions.
"The Argentineans are tough on him, but he cannot do everything on his own."
Umtiti, who is paired with Real Madrid's Raphael Varane in defence, should have a key role against Messi if he is well fed by his team, which was not always the case in the group phase, which Argentina escaped with a last-gap 2-1 win against Nigeria.
"(Umtiti) does not feel the pressure. He's ice-cool, he's zen," said France midfielder Thomas Lemar.
(Writing by Julien Pretot; Editing by Christian Radnedge)
