The move means that each player must miss at least 10 games and 24 days. The Blackhawks also gain some financial flexibility to go over the salary cap while the players are out.
Toews announced before training camp that he was out indefinitely due to an illness. He did not disclose what that was, and it's not clear how long he will be out.
Dach, the former No. 3 pick in the draft who was starting his second year in the league, fractured his wrist at the world junior tournament and is expected to miss the season.
The Blackhawks also announced that Brent Seabrook, who had offseason surgery on both hips and a shoulder, remains on injured reserve.
The Blackhawks opened their season Wednesday with a 5-1 loss to the defending-champion Lightning.