Motta has publicly expressed his desire to join Atletico Madrid before the close of the transfer window but the two clubs have yet to agree a fee for the Italy international.
However, Blanc has stated that Motta is only sitting out the meeting with Lyon because of a groin problem, and added that Argentina duo Javier Pastore and Ezequiel Lavezzi are not yet match fit having been given an extended summer holiday following their participation in the Copa America.
"I do not think that Argentines will attend the game tomorrow," the PSG boss told reporters on Friday. "They arrived late.
"Motta, meanwhile, has a groin injury. He will not participate in tomorrow's match.
"But can be confident due to our good preparation. However, we know that Lyon are also well prepared.
"But have players who can make a difference individually and I hope that all of them will face Lyon tomorrow."
PSG are on the verge of completing a deal for Manchester United attacker Angel Di Maria, with the proposed €62 million transfer expected to be completed in the coming days.
Blanc refused to be drawn on the speculation but did admit the French champions are seeking reinforcements in order to strengthen their bid for European glory.
"We are trying to improve the team so that we can be successful in the Champions League," the World Cup winner added.
