The Swedish striker is expected to be injured for four weeks but his PSG coach says Edinson Cavani can step into the void.
The Swede limped off during the 3-1 win over Chelsea midweek and PSG president Nasser Al-Khelaifi believes he will be out for around four weeks.
Blanc is still uncertain as to how long he will be without the former Barcelona man but says he will not be tempted to alter his approach.
"He has a muscular lesion. He is unavailable for the coming weeks for an unspecified amount of time," he told reporters. "Unless the injury gets worse, he will be available to finish the season. It's hard to tell because it's still fresh, it will depend on how the injury evolves. Our philosophy and our tactics will not change."
Blanc also believes that out-of-form striker Edinson Cavani can step into the void left by Ibrahimovic.
"Cavani is a striker who scores goals and is also a good defensive replacement," he added. "Cavani has nothing to prove. This is a great goalscorer who was injured. He will back to goals, I am sure."