While the Spain international talked up Messi, he hopes his team-mates can find a way to stop the 30-year-old — who has failed to score in eight games against Chelsea.
"Messi is the best player in the world, but he's not invincible," Pedro told UK newspapers.
"Obviously, it's Barcelona. It's Leo Messi. It's very difficult to stop this guy because he's very quick, very clever. But, look, it's not impossible.
"He's on another level. No one can do what he does. For this reason, to have played with him is special. Special for me, and something to tell my sons in the future because, probably, he'll be considered the best in history."
Chelsea stunned Barcelona in the semi-finals in 2011-12, on the way to their one and only Champions League crown.
Pedro, who headed to Stamford Bridge in 2015, said he still remembered the tie, which the Premier League outfit won 3-2 on aggregate.
"I remember these games so well. Chelsea were always horrible opponents, very difficult in these games: compact, strong in defence, pressed very well," he said.
"For that reason, we always found it difficult against them.
"For the players of Barcelona, they'll be thinking this tie is going to be very tough, this game for them, because Chelsea are strong. Chelsea are compact, and it's never easy to play against us."