Lewandowski announced in January that he would be departing for Bayern Munich upon the expiration of his BVB contract this summer and he has wasted little time in impressing his new employers in pre-season.
However, Blaszczykowski insists that Dortmund, who have moved to cushion the blow of Lewandowski's exit by signing forwards Ciro Immobile and Adrian Ramos, can cope without last season's Bundesliga top scorer.
"It's normal in this business that some top players leave but Borussia still lives on because new good players arrive," he told Kicker.
"Everyone decides for themselves what is right for him. Nuri Sahin, Shinji Kagawa, Mario Gotze and Robert Lewandowski now have left Dortmund but Borussia but still lives on, because every year good new players have come.
"We will be helping Adrian Ramos, Ciro Immobile, Matthias Ginter and Ji so that they can be integrated quickly and we find ourselves as a team."
Blaszczykowski, of course, has been out of action since January with cruciate ligament damage but he is confident of soon being in a position to help BVB reclaim the Bundesliga title from Bayern.
"I feel good. Although I'm still not completely pain free, I realise that it will get better by the day in training," he added.
"I am pleased with how [the recovery] has developed and I am glad that it will not take a long time."