The 22-year-old South Korea international was outstanding in midfield for Lennon's side and he capped off a fine performance with a 63rd-minute strike.
"He's a very important player to us. I rate him very highly. He can go on to be anything he wants to be," Lennon told The Telegraph.
"We think he is a class player and we're glad he's here."He added: “Ki has been very consistent over the past 18 months. He's developing nicely into a class player.
"He had good presence and good composure on the ball. He has a goal or two in him and his passing range is excellent."