ST. PAUL, Minn. -- It was a big night for the Chicago Blackhawks, who completed a sweep of the Minnesota Wild in the Western Conference Second Round on Thursday. But the victory came with a price.

Defenseman Michal Rozsival left Game 4 with a lower-body injury at 6:37 of the second period and didn't return. Asked for an update after the series-clinching 4-3 victory, the answer by Blackhawks coach Joel Quenneville was brief but telling.

"Tough loss," he said. "Doesn't look good."

Quenneville said something similar on Feb. 24, when right wing Patrick Kane crashed hard into the boards and fractured his left clavicle. Kane needed surgery a day later and missed the final 21 games of the regular season.

Rozsival, 36, fell awkwardly in the neutral zone while skating backward to defend Wild forward Thomas Vanek after Nino Niederreiter lifted the puck from the Minnesota end into the Chicago zone. Play continued for 14 seconds with Rozsival unable to get up, and Chicago goalie Corey Crawford made a right-pad save to deny Vanek on a breakaway.

Rozsival could not put weight on his left leg and needed help getting off the ice and to the locker room.

"You hate to see your teammates in pain like that," left wing Patrick Sharp said. "I'm not sure what the diagnosis is or how he's doing. I haven't even seen him yet, but to see the way the defense stepped up and played shorthanded, from basically the halfway point of the game on, was impressive. Credit them."

After play resumed, Minnesota forward Erik Haula scored at 6:41 to cut the Blackhawks' lead to 2-1. The Wild continued to apply pressure, seeking a game-tying goal, but Chicago managed to fight through the momentum swing and got out of the period with the lead.

"It's a faceoff in our end, and it's just a bang-bang play [for Haula's goal]," defenseman Duncan Keith said. "That's just execution, and I think you move forward. Obviously, nobody wanted to see a guy get hurt, but those types of things have happened before and you've got to keep playing. They won the draw and got a shot and it was a quick play."

Quenneville had been using primarily five defensemen in the series, spotting 40-year-old Kimmo Timonen. Following Rozsival's injury, Quenneville pared the playing group to basically the top four in the third period. Timonen played seven shifts after Rozsival was injured, three in the third period for a total of 1:43. He finished the game with 8:25 in ice time.

Timonen played 5:44 in Game 3, with one 40-second shift in the third, played 6:57 in Game 2, and 10:49 in the Blackhawks' series-opening 4-3 win at United Center on May 1. Quenneville didn't reveal what he plans to do if Rozsival can't play in the Western Conference Final, but it's likely that David Rundblad will get the first opportunity.

The Blackhawks also have Kyle Cumiskey and rookie Michael Paliotta as options.

Rozsival played 7:16 in Game 4 and was averaging 18:34 playing mostly with Keith on the top pairing through the first two series. It's a significant loss if his role can't be adequately filled, and would put a big physical tax on the top four of Keith, Brent Seabrook, Niklas Hjalmarsson and Johnny Oduya.

"You've just got to look at the guys who played the big minutes tonight," Quenneville said. "They were rock solid."

Keith again led the Blackhawks, and all skaters, with 29:39 on 34 shifts. He finished with a plus-2 rating and said he and the others will be ready to soak up as many minutes as needed in the next round.

"Whatever happens ... happens," Keith said. "I've played with different guys the whole year and over the last few years. We're all in good shape, obviously. We've just got to be smart."

They Blackhawks get the chance to rest while the Calgary Flames and Anaheim Ducks play the rest of their second-round series; the Ducks lead 2-1 entering Game 4 at Calgary on Friday (9:30 p.m. ET; NBCSN, SN, TVA Sports). Losing Rozsival is a big blow, assuming it will be long-term, but sweeping the Wild provides time to recover physically and devise a replacement strategy.

"Every game's different, but in the playoffs we get grooving and in-between game days they get rest and you get yourself ready for the next game ... there's enough time to prepare for the following game," Quenneville said. "I think that group, for the most part, they've played some significant minutes in a lot of big games and we'll see how it all turns out and works out. But I think a couple of days off here for the group right now will be nice and we'll see what happens."