The German midfielder went off just before half-time in a closely-fought game at the Amex Stadium and Freedman told the official NFFC website afterwards that it looks as though the player has sustained a broken foot.
Kazenga LuaLua broke the deadlock five minutes after the break, a goal which then prompted Forest into their best spell of the match with Tyler Walker causing problems when he was sent on to partner Dexter Blackstock in attack.
Freedman was pleased with that response but admitted the opening 45 minutes had belonged to the hosts.
Walsall are the Reds' next opponents in the League Cup but the priority ahead of the home league opener next Saturday against Rotherham on Saturday will be new additions to a squad that already looks stretched.