"The two players cannot be compared," he said in response to a question about it at the press conference prior to the quarterfinals of the Champions League.
"Robert Lewandowski is a world-class player. As a forward, he guarantees us goals and creates goals. Messi has been the best in the world in recent years. He is an exceptional player like never before," he added.
However, Flick emphasized that Bayern is not playing against Messi, but against Barcelona, and highlighted the quality of other players such as Uruguayan Luis Suárez, Sergio Busquets, Gerard Piqué, "and a great goalkeeper like (German) Marc-André ter Stegen."
"We have great respect for Barcelona because they have dominated football for years. Many coaches and teams have been inspired by their football. La Masía is an example of player development. They have great players, in addition to Messi," he said.
Regarding how to control Messi, he said that naturally he had developed a plan that he would not go into details about, but said that the key is to play as a team to put him under pressure.
When asked if Friday's match is special for Thiago Alcántara because he is playing against his former team and probably playing his last matches with Bayern, Flick said that the commitment was special for everyone.
"Now the focus is only on this match. What comes next doesn't matter. It's not just a special match for Thiago, but for all of us. Competing against the best is what makes us grow as a team," he said.