The Germany attacker is currently on-loan this season with Tottenham.
"Timo Werner is currently at Tottenham and we spoke to his agent two or three weeks ago. I don't think the loan is going as well as we had hoped," Schäfer told RB Live.
"(We will) think about Timo Werner and all the players who will return in the summer. We want to have a team on the pitch that is in line with what I have already said several times.
"We need to bring in new blood, a new spirit. We need to bring back the attitude, the liveliness, the brutal energy that has set us apart from other clubs."
Leipzig is sixth in the Bundesliga with seven rounds left to play and is chasing a Champions League spot.
Werner is on loan to the end of the season and has a contract with the German club until the summer of 2026.