Krüger, who starts for the Lyn Ski, took part in juniors and FIS races from 2010 to 2013 . At the Nordic Junior World Ski Championships 2013 in Liberec , he reached fourth place in the skiathlon and over 10 km freestyle. He won silver with the relay. His first World Cup race was in Oslo in March 2013 , which he finished in 43rd place in the 50 km mass start race. In the 2013/14 season he took part in the Scandinavian Cup , where he mostly finished in midfield. At the beginning of the 2014/15 season he reached 21st place in the overall ranking at the Nordic Opening and thus also got his first World Cup points. At the U23 World Championships in Almaty in 2015 , he won silver in the 15 km freestyle. In the 2015/16 season he came in five individual World Cup competitions, four times in the points. The 11th place in the 50 km mass start race in Oslo was his best season position in the World Cup. In February 2016 he won the gold medal in the 15 km freestyle at the U23 World Ski Championships in Râșnov . At the Norwegian Championships in 2016 he won gold in the relay and bronze in the 10 km freestyle. After 11th place in the World Cup Mini Tour in Lillehammer , he achieved five top ten placements in the 2016/17 Tour de Ski , including third place in Toblach over 10 km freestyle, eighth place in the overall standings. In January 2017, he won his first World Cup victory with the relay in Ulricehamn . At the beginning of February 2017 he was the Norwegian relay champion in Lygna . At the end of the season he finished 38th in the World Cup finals in Québec and reached 17th place in the overall World Cup and 15th place in the Distance World Cup.
At the beginning of the 2017/18 season, Krüger achieved 16th place in the Ruka Triple and won his first individual World Cup victory in Dobbiaco over 15 km freestyle. In January 2018 he became Norwegian champion in the 15 km freestyle. In the following month, despite a fall in the course of the race, Krüger won the Olympic gold medal in skiathlon. This was followed by the silver medal in the 15 km freestyle race and the gold medal with the relay. At the end of the season he came in 24th place at the World Cup finals in Falun and finally reached 14th place in the overall World Cup and eighth place in the Distance World Cup. After eighth place in the Lillehammer Triple at the beginning of the 2018/19 season, he took third place with the relay in Beitostølen . At the Tour de Ski 2018/19 he was two second places and third in the overall standings. In January 2019 in Ulricehamn he came third with the relay and second in the 15 km freestyle. At the beginning of February 2019 he became the Norwegian relay champion in Meråker . At the season highlight, the Nordic World Ski Championships 2019 in Seefeld in Tyrol , he finished fifth in the 50 km mass start race. At the end of the season he finished seventh at the World Cup finals in Québec and finished the season in fourth place in both the overall World Cup and the Distance World Cup. At the beginning of the 2019/20 season, he won the 15 km freestyle in Davos and came fifth in the 2019/20 Tour de Ski . He won the final stage over 10 km. This was followed by third place in the pursuit in Nové Město and second in the skiathlon in Oberstdorf . He finished the 2020 ski tour with second place in Östersund over 15 km freestyle, in second place. At the end of the season he finished second in the 50 km race on Holmenkollen and came fourth in both the overall World Cup and the Distance World Cup.