"Calvin de Haan and Brent Seabrook each underwent surgery today on their right shoulder," team physician Dr. Michael Terry said in a statement. "Both surgeries went well. We anticipate Calvin ready to return in four-to-five months. We anticipate full recovery for Brent following successful completion of his additional surgeries. Exact recovery time will be announced at that time."
De Haan suffered a right shoulder injury Dec. 10 against the Vegas Golden Knights and has not played since. He underwent offseason surgery on the same shoulder.
"From the [coaching] perspective, we're focused on the players we have and find a way to get it done," coach Jeremy Colliton said Friday. "But of course those guys are really big parts of the group, both on and off the ice. A lot of leadership and solid, dependable-type players, which, of course, we're going to miss."
De Haan was acquired from Carolina in June, along with forward Aleksi Saarela, for defenseman Gustav Forsling and goalie Anton Forsberg. De Haan was supposed to shore up a defensive unit that was the Achilles' heel of the team last season. Instead, his season ends with one goal and five assists in 29 games.
In addition to the shoulder surgery, Seabook will undergo surgeries on both hips over the next two months.
He has not played since Dec. 15 and finishes with three goals and one assist in 32 games this season.
"Such a huge part of our room," forward Patrick Kane said. "So hopefully he gets his injuries fixed and comes back better than ever."
Seabrook, who is under contract through the 2023-24 season at an average annual value of $6,875,000, missed a total of nine games over the previous six seasons.
"He's battled through these injuries for a long time," defenseman Duncan Keith said. "Anybody else, they probably would have been missing a lot more time than that over the course of the last several seasons. It shows the kind of mentality and the type of person that he is."
Seabrook and de Haan were placed on long-term injured reserve, giving the team some salary cap relief.
The Blackhawks also announced that forward Brandon Saad will miss about three weeks with a right ankle injury. He had been placed on injured reserve earlier this week.
Saad is second on the team with 11 goals and fifth with 19 points.
Fellow forwards Andrew Shaw and Drake Caggiula are on LTIR due to concussions, though Caggiula has been skating and could return soon. Rookie defenseman Adam Boqvist missed Friday night's 5-2 victory over the New York Islanders because of a right shoulder injury.
"I don't manage expectations,'' Colliton said. "We expect to win. We expect to compete, give ourselves a chance with how we play.''
The Blackhawks are having another up-and-down year after missing the playoffs the past two seasons. They are last in the Central Division but won at Winnipeg and Colorado last week before losing 7-1 at home to the lowly Devils on Monday.
Chicago's defense has given up the seventh-most goals in the league, has the worst expected goals against and has given up the third-worst scoring changes against. The team is hovering around .500 in large part because of the stellar goaltending of Robin Lehner and Corey Crawford.
Information from The Associated Press was used in this report.