Kosicke acts as Nagelsmann's agent and has cooled talk of the coach moving to Bayern Munich this summer.
He told Sport1: "Neither Bayern has asked Hoffenheim, nor Julian Nagelsmann has heard from Bayern. There's been some enquiries for him. But that happens with many coaches, not just him. Besides, Julian has a contract.
Kosicke added: "The club of course also sets him up by selling good players.
"You have to think about whether this will work out well in the long term."