The Spain international joined City from Valencia and is beginning to show his world-class form whilst receiving strong praise from his new manager.
"For David Silva it is easy to play football," said Mancini. "Everything is easy for him."
Mancini added that his team were able to get a good result with some strong play despite dropping their guard for a period in the second half.
"As a team, I thought we played very well in the first half," he added.
"We scored two goals and did some good things. But we were ordinary in the first 20 minutes of the second.
"For a little while I was a bit afraid because I thought Lech could cause some problems. But the third goal finished the game."