Maatta, a 26-year-old defenseman, scored 17 points (four goals, 13 assists) in 65 games this season and six points (three goals, three assists) in nine postseason games for the Blackhawks. Chicago was eliminated from the best-of-7 Western Conference First Round in five games by the Vegas Golden Knights.
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A two-time Stanley Cup winner with the Pittsburgh Penguins (2016, 2017), Maatta has scored 124 points (29 goals, 95 assists) in 427 regular-season games and 27 points (five goals, 22 assists) in 78 postseason games for the Penguins and Blackhawks. He has two seasons left on a six-year contract signed with Pittsburgh on Feb. 26, 2016.
"Olli is a well-rounded player who will fit well with our group of defensemen," Los Angeles general manager Rob Blake said. "He is a young player that already has a lot of valuable NHL experience, including a pair of Stanley Cups, and we look forward to having him join our organization."
The Kings finished 14th in the Western Conference and did not make the Stanley Cup Qualifiers. They have missed the postseason two straight seasons and three of four.
Morrison, a 23-year-old center, has yet to play in the NHL. He scored 19 points (six goals, 13 assists) in 17 games for Fort Wayne of the ECHL this season.