The former Celtic left back is still finding his feet with the Gunners, as he has been in and out of the starting lineup.
But Rodgers believes that after a few months, Tierney will find his best form and make the left back position his own.
The Leicester boss worked with Tierney at Celtic for the past few years.
"As a player, in the first week working with him, I could see after two or three days why there was a lot of clamour for him," said Rodgers to reporters.
"From that moment he was absolutely brilliant for me. He became stronger, more powerful, very aggressive in his game.
"He worked hard every single day but he was also a strong boy mentally, and he had a lot of good mentors. Scott Brown was an incredible captain for me, and he [Tierney] took on that mantle to try and be like him.
"Every day in training he was very focused on becoming better, and obviously he loved Celtic as a club. He supported the club, and that gave him that extra one per cent every time he played.
"So as a player he was fantastic, and he captained the team for me on a few occasions as well, but also a great boy, very humble, just wanting to be the very best he can be."