Cavani was introduced late on during PSG's Ligue 1 opener at Montpellier, but was unable to find a late winner as the visitors were forced to settle for a 1-1 draw.
Blanc thinks that the Uruguayan forward needs time to find form and fitness for PSG, but insisted that his impact was positive and helped press Montpellier further into their own half.
He told reporters in his post-match press conference: "He [Cavani] created depth. He also had a great opportunity that was blocked by a defender. He will give us the depth we need.
"He is not 100%, far from it. But he is still an important player and, in particular, a goalscorer. This is a player who has had about 10 days of preparation. He now needs to play.
"There will be no friendly matches for him to reach perfect condition so therefore it must be done in an official match."