Manolas, 26, has been a colossal figure for the Italian outfit this season, featuring in 30 games across all competitions in the heart of the Giallorossi defence.
However, ahead of their first leg UEFA Champions League quarter-final tie, the Greece international concedes the attacker he's coming up against is unstoppable.
"Guardiola is right when he says there's no way to stop him [Messi]," Manolas told Il Giornale. "Even if you could fix that somehow and maybe block him off, there are 10 others that can hurt you.
"Of course, Barcelona are still something else without Messi. We'll have to do our best. They're favourites...but you never know."