The club is still searching for a replacement for Yan Diomande following his club-record departure to Real Madrid.
Speaking to Magenta TV on the fringes of Saturday's 3-1 pre-season defeat at Bayern Munich, the new head coach made clear the squad rebuild is an ongoing process.
"I speak with Marcel Schäfer every day. We're still working on it in this transfer window. He has work to do. We still need to bring in a few more players," Demichelis said.
The Argentine admitted Diomande's exit "hurts", with the Ivory Coast international having completed a move to Real Madrid reported to be worth a club-record fee of around €125million, potentially rising to €140million with bonuses, on a contract running until 2033.
Diego Moreira has emerged as Leipzig's leading candidate to fill the void left on the wing, with Sky Sports reporting the two parties have reached a verbal agreement over personal terms on a contract until 2031, though talks with his club, Racing Strasbourg, have proven difficult over the transfer fee, with the French side reportedly holding out for a figure as high as €60-70million.
RB Leipzig have also been credited with interest in midfielders Samir El Mourabet, also of Strasbourg, and Kaishu Sano of Mainz 05, as well as AC Milan forward Christopher Nkunku, as Demichelis looks to reshape his attacking options following his appointment as head coach this summer.
With the proceeds of the Diomande sale swelling Leipzig's transfer budget, the club is expected to remain active in the market over the closing weeks of the window as it seeks to strengthen multiple areas of the squad.