The Blues will face the five-time Ballon d'Or winner once again when they host the Catalan side for the first leg of their last-16 clash at Stamford Bridge on February 20.
Although Messi has some bad memories of trips to Chelsea, having missed a penalty against them in the 2012 semi-final that saw the Premier League side advance to the final with a 3-2 aggregate win.
Messi may have been left devastated by that incident, but Morata has warned Antonio Conte's side that containing the Argentine icon is dangerous enough to leave Chelsea in tears next week.
"Messi can't be stopped," the former Real Madrid striker told Movistar+.
"If we can get a good result here, we have to play a defensive game with spaces and try to bother them as much as possible."
The Spaniard is not the only Chelsea star to sing Messi's praises recently.
Eden Hazard recently insisted the 30-year-old is "not from this world" and urged the Blues to be careful against the Camp Nou outfit.
Messi has already scored 27 goals in 36 games in all competitions this season and is the top scorer in La Liga with 20, but has netted just three times in six Champions League appearances.