The two sides meet in the first leg of their Europa League last 16 tie on Thursday with the Spaniard expected to lead the front-line for the Basque-based La Liga side.
And the 27-year-old has even gone as far as claiming it will be one of the highlights of his career so far as the club travel to Old Trafford ahead of the second leg at San Mames.
"This round against Manchester United will be a key moment in my sporting career so far. After the World Cup in 2010 and the Copa del Rey final coming up, this is the most important match ever for me," he said.
"To play at Old Trafford is a dream challenge for any footballer and now I am dreaming of success on that pitch.
"Matches like this are a special test of my ability."
The powerful target-man has been subject to increased speculation regarding his future in recent months, and he admits he grows weary of the talk linking him with a move to England.
"People have said that my style is very English, now we will be able to test that," he said.
"I am tired of talking about my future, rumours about England and Spain, but I am calm and just focus on my play as anything else would damage my performance."
Llorente admits the Red Devils are favourites to secure safe passage to the quarter-finals of the competition, but he insists he and his team-mates travel to Manchester without fear.
"It is normal that people make Manchester United favourites, but we go to England with no fear," he said.
"We go to enjoy the game but also we are thinking about our mission which is to get a good result for the second leg at the San Mames.
"But to go up against the defenders of United will be about passion, to come up against Rio Ferdinand and to play against Ryan Giggs is unique."
