The midfielder was brought in on a free transfer during the summer transfer window, after his contract at Crystal Palace expired.
And Lees says that he was excited when he found out that he would be linking up with a player of the Scotland international’s quality.
Lees knew all about Bannan’s creativity, but the defender has been pleasantly surprised by the amount of effort the 25-year-old puts in during matches.
“When Barry [Bannan] signed, I knew he had real ability so I was excited to see what he would offer," he said. "Straight away it became clear that he was a top player.
“I have been pleasantly surprised to see how hard he works off the ball. A lot of players with his ability, vision and passing range usually have one side to their game where you have to carry them a bit but not with Barry. His work rate is phenomenal so that’s good to see.”
Bannan has played a key role for Wednesday this season, and he has come into his own over recent weeks.
The attacking midfielder has set the tone for the Owls with his displays and he is rapidly becoming a fans’ favourite at Hillsborough.
Wednesday have managed to go unbeaten in their last 11 matches, and they could move into the play-offs places in the Championship table if they can beat Charlton Athletic.