2008-09: Ludwig Karlsson skated in Sweden's U20 SuperElit league as a 17-year-old — splitting the season between Linkoping's U20 and U18 squads. In 23 SuperElit games he scored 5 goals with 7 assists and was +7 with 16 penalty minutes. Linkoping defeated Leksands before falling to Brynas in the playoff quarterfinals. Karlsson scored 4 goals and was +1 with 4 penalty minutes in five playoff games. In nine U18 games, including 2 playoff contests, he scored 4 goals with 5 assists and had 6 penalty minutes.
2009-10: Karlsson moved to North America to play for the USHL's Green Bay Gamblers. In 58 games he scored 8 goals with 21 assists and was +15 with 16 penalty minutes. The Gamblers finished first in the East Conference and won the USHL's Clark Cup. Karlsson scored 1 goal with 2 assists and was an even plus/minus with 2 penalty minutes in 12 playoff games. In March 2010 he committed to playing college hockey at Northeastern University in 2011-12.
2010-11: Karlsson returned to Green Bay for a second season with the Gamblers. He scored 13 goals with 25 assists in 56 games and was +8 with 14 penalty minutes. The Gamblers finished second in the Eastern Conference and lost to Western Conference champion Dubuque in the Clark Cup finals. Karlsson was -3 and scored 2 goals with 3 assists in 11 playoff games.
2011-12: Karlsson was Northeastern University's leading scorer as a freshman. In 32 games he scored 10 goals with 16 assists and was +3 with 8 penalty minutes. The Huskies finished tied with Massachusetts-Amherst for eighth in Hockey East but missed the playoffs on tiebreaker criteria.
2012-13: After a sensational freshman campaign, Karlsson followed it up with an impressive start to his sophomore season before suffering a season-ending wrist injury in January. He played in just 17 games, posting 5 goals with 3 assists and finished -2 with 4 penalty minutes. His most memorable game was on November 10 versus Alabama-Huntsville when he netted a pair of goals in guiding the Huskies to a 3-0 victory. Karlsson signed a two-year entry-level contract with Ottawa as a free agent in July of 2013, foregoing his final two years of college hockey.
Karlsson is a dynamic winger blessed with size (6’2 and 194 pounds) and terrific puck-moving ability. Although Karlsson is a left wing, he spent considerable time playing on right wing this past season as well, excelling at both positions. Karlsson possesses soft hands and is very poised with the puck. He does a good job of following and staying with plays and is particularly dangerous around the net. Karlsson has the ability to score in bunches and his passing skills are excellent. He is equally good at both scoring goals and setting up plays. Simply put, Karlsson knows what to do with the puck when it’s on his stick. One of Karlsson’s best attributes is his shot. He possesses a hard shot with a quick release. But it is the accuracy of his shots that is most notable here. When Karlsson returned to the Huskies lineup on February 1, 2013, it was noticeable that his injury had not fully healed because his shot lacked its usual accuracy as well as velocity.
Another of Karlsson’s best attributes is his skating. He skates with long, smooth strides and has really nice edges. He does a good job of consistently keeping his feet moving – an area that vastly improved this season. He possesses quick feet and good acceleration as well.
One notable area where Karlsson made great strides in his development during his sophomore season was in his ability to use his large frame more effectively. This was particularly evident in his ability to get inside positioning on opposing defenders. Karlsson’s willingness to play the body more and his added strength have made him more effective in protecting the puck. He also uses his long reach quite well in stripping pucks as well.