The La Liga leaders were heading out of the competition before the Argentine was summoned from the bench and went on to play a crucial part in Pedro's equaliser, which sent Barca through on away goals at the Camp Nou in the quarter-final second leg at the expense of Paris-Saint Germain.
Pique is adamant that Messi, who was tipped to miss the game with a hamstring injury, can make a difference even if he is only half fit.
"We are talking about the best player in the world. It doesn't matter if he is a little bit injured, he can change everything and he did again," Pique told Sky Sports News. "We are really lucky and really proud to have Leo on the team and we have to use him when we are struggling a little bit.
"We knew that for us to have Leo on the pitch was really important. He is our reference, he can score he can pass, he can do everything and he helps us a lot.
"If you have him you have to use him and try to use the best part of him and he helped us a lot."
Barcelona are joined in the semi-finals by Real Madrid, Borussia Dortmund and Bayern Munich.