While we don't know the length yet, the Hawks know that they're going to be playing a few games without their main main in defense, Duncan Keith.
It's a huge loss, arguably bigger than Toews. Whereas the Hawks had three other genuine stars at forward to make up for Toews's absence in Hossa, Kane, and Sharp, at defense the Hawks only have Keith's usual partner in Seabrook who can play up to an All-Star level. And as we've seen in the past, Keith is the bellwether for this team. When he's bad, the Hawks are bad. When he's good, the Hawks are good. He's that vital.
So what will the Hawks do? Couple ways they can go here. They can move Nick Leddy up to the top pairing with Brent Seabrook, which they did in the middle of the year when Dylan Olsen was brought into the lineup. Leddy's game is the one that most mirrors Keith's, with the speed and transition. But Leddy's defensive gaffes could be far too costly to toss him out against the opponent's main threats, and they would be aching to expose him. If this were to happen, Leddy would really have to step up his game for however long Keith is sitting.
The Hawks could also opt to not break up what has been a very steady second pairing in Leddy and Johnny Oduya, under the theory that one pairing's going to be worse anyway so why make two worse? In that scenario, Niklas Hjalmarsson would play with Seabrook, which he's done in the past. But those two don't have a lot of foot-speed, and Seabrook can't cover as easily for Hjalmarsson's yippiness with the puck. It would be defensively strong and block a lot of shots, but it would have a hard time getting the Hawks transition game going or joining in the rush.
There is the option of moving Oduya up with Seabrook, as his more steady play would fit better against top opposition. But that would leave Leddy to play with Hjalmarsson, and we've all see how that can go.
Some of this depends on if Steve Montador, who practiced today, can return to the lineup and round out the bottom pairing. If he can, Quenneville can distribute the minutes a little better and hopefully keep the roof from caving in. Sami Lepisto's injury is a real blow now, because he also have plus-feet to fill in on one of the bottom pairs that will be vacated by whoever has to fill in for Keith.
Whatever they choose, it's less than optimal.