"We've been meeting over the past couple days, and Niklas [was] a big part of our success last year," Chicago general manager Stan Bowman said. "He's part of our core that is going to be together for a long time."
Coach Joel Quenneville praised Hjalmarsson's dependability.
"I'm happy for us, I'm happy for Nik," Quenneville said. "He's a very dependable defenseman. His character is great, and he's everything you look for in a defenseman."
"You can never have enough defenseman around, and having a predictable defenseman around at a young age is hard to find. Nik fills that need and void that could have been there."
The Hawks had until Friday to match the offer, or they would have received first-round and third-round picks in next year's draft. The Sharks had targeted Hjalmarsson to replace retiring captain Rob Blake.
"We appreciate Niklas' interest in coming to San Jose and we respect the process as it has unfolded," said Sharks GM Doug Wilson, a former Blackhawks defenseman himself. "We will continue preparing our team as we head towards the start of the 2010-11 season.
"As we have said in the past, we are always looking at ways that we can improve our team and we will continue to do so moving forward."
Bowman was somewhat surprised by the Sharks' offer.
"Offer sheets don't happen very much, so yeah, it was a surprise," Bowman said. "It is used occasionally, so we knew it was a possibility."
Bowman had said key restricted free agents wouldn't be leaving. Bowman has traded several members of the Stanley Cup champions as he battles salary cap constraints.
Hjalmarsson earned $660,000 last season. The Swede averaged a just under 20 minutes of ice time per game in the regular season and 21 minutes in the playoffs as the No. 4 defenseman behind Norris Trophy winner Duncan Keith, Brent Seabrook and Brian Campbell.
"He gets overshadowed maybe because we're got some other superstars there," Bowman added. "But he was really effective for us all year long. His steady play is something that only is going to get better."
Goaltender Antti Niemi also is a restricted free agent. His arbitration date has been set for July 29. It was thought that the Hawks would wait until Hjalmarsson's deal was set before dealing with Niemi.
"We're still negotiating with Antti," Bowman said. "It's a back and forth. We're trying to get it done so we'll keep at it.
"It's a negotiation. Both sides have their points of view so hopefully it works out."
Since winning their first Stanley Cup in 49 years, the Blackhawks already have shed seven players remain on under the NHL's $59.4 million cap for next season. Among those who have left are defenseman Brent Sopel and forwards Dustin Byfuglien, Kris Versteeg and Andrew Ladd.
Bowman didn't rule out the possibility that the Blackhawks might have to trade yet another player -- even Niemi -- to remain under the cap. The team's situation is complicated by approximately $4 million performance bonuses earned by players last season that apply to the club's 2010-11 cap.
"We're going to have to work things out," Bowman said. "We've been saying all along our goal is to keep our core together. We've been trying to hit that point and Niklas is part of that core. I think you win with defense. I think the success of our team is that we've got some very skilled forwards, but they also get the puck a lot. We want to keep that part of our game intact."
Jesse Rogers covers the Blackhawks for ESPNChicago.com. Information from The Associated Press was used in this report.