Chelsea chiefs are considering moving for Bailey this summer, well aware his price is skyrocketing.
Bayer chief Jonas Boldt stated: "If he keeps working hard, stays on the ground and develops in an environment like Leverkusen, why not grow to the level of (Ousmane) Démbelé?
"Why should we put a price tag on Leon? We have no plans to hand him over. Our goal is to take him into the Champions League and develop him."
Bailey, reports Kicker, still has a soft spot for Chelsea, having admitted he dreamed of playing for the Blues just over two years ago.
The winger joined Bayer last year from Genk for €12m.