According to Goal, Chelsea, now managed by Thomas Tuchel, are interested in Sule, but Bayern boss Flick has revealed how the defender's versatility makes him an invaluable option in his squad going forward.
"Niklas is an absolute option, whether in the centre or full-back position. He did well at Schalke [in a 4-0 win last month when Sule played at right-back]. Don't forget that he had a long injury," Flick told reporters.
"Niklas is a fast player who is calm on the ball and helps shape the game from the back. Given his size, he has absolute strength and I'm glad he's on our team.
"We will see how everything develops and how he sees his future. I am satisfied with his development, you can rely on him."
Sule, who joined the Bundesliga champions from Hoffenheim in 2017, has made 12 appearances in the league this season, with only five of those from the start.