The former Juventus goalkeeper came out of retirement to join Barca as a replacement for knee injury victim Marc-Andre ter Stegen.
Lewandowski was key to the deal for his former Poland teammate and said from the nation's training camp: "Before leaving Juventus and retiring he told me that he would only continue playing if Barcelona called him.
"In this period in which he has rested he has regained freshness, and he will only need two weeks of training to get back in shape. He is calm and peaceful.
"I'm sure he will make a great contribution to the team. When a new player arrives, you have to introduce him to the club environment. The same goes for Wojciech, but with his experience and his attitude towards life, he will settle in very quickly."