Lewandowski, 36, has been given a new lease of life under new coach Hans-Dieter Flick .
There were two more goals as Barcelona overcame Young Boys 5-0 in the Champions League last night.
However, Lewandowski was annoyed when he was substituted. It is a good sign, according to former sporting director Cruyff.
"Lewandowski dreamed of playing for Barcelona, that was the key to his signing," he said.
"When you see a 36-year-old angry at his substitution because he wants to score a hat-trick, that's when you can see a player who is still obsessed with scoring goals."
Cruyff was also happy seeing Inigo Martinez score on the night.
"Many fans only watch matches on the pitch, but there are things that happen off the pitch as well," he said.
"Iñigo Martinez is a leader off the pitch, in a dressing room full of youngsters. His experience is perfect for that role. Whether he is playing or not, Iñigo is always there to work hard."