2008-09: Johan Gustafsson played for Farkestad in the J18 Elite and Allsvenskan brackets. In games for the Elite team, he registered a 1.94 goals-against average and a .910 save percentage. In 14 games of Allsvenskan play, Gustafsson finished with a 1.63 goal-against average and a .936 save percentage. Gustafsson was named to Sweden's Under-18 WJC squad. He played in 2 games in that tournament, registering a 1.00 goals-against average and a .964 save percentage.
2009-10: Gustafsson played most of his games for Skare BK in Division I, posting a 2.86 GAA and 1.84 save percentage in 26 games. At the U-18 World Championships, he posted a 2.02 GAA and .918 save percentage in 4 tournament games.
2010-11: Gustafsson played for Vasteras in Sweden's Allsvenskan (second league); sharing the starting duties with veteran Daniel Sperrle Jonsson. Gustafsson had a 2.30 GAA and .911 save percentage with two shutouts in 26 games for fifth-place Vasteras. He appeared in two of six post season games in the pre-Kvalserien tournament and was 1-1 with a 2.94 GAA and .867 save percentage. He also skated in seven games for Vasteras' U20 team and had a 2.83 GAA and .913 save percentage.
2011-12: Gustafsson shared the goaltending duties for Swedish Elitserien regular season champion Lulea with veteran David Rautio and was in net for gold medal-winning Sweden at the 2012 U20 World Junior Championship. Gustafsson had six shutouts and finished with a 1.68 goals against and .932 save percentage in 29 games. Lulea was upset by AIK in the quarterfinals of the Elitserien playoffs; four games to one. Gustafsson had Lulea's only win in the opening game of the series and was 1-2 with a 3.36 goals against and .884 save percentage in three playoff games. Playing in five games for Sweden, he was a perfect 5-0, including a 17-save shutout in the gold medal game against Russia. He had a 2.20 goals against and .888 save percentage in the tournament. Gustafsson signed a three-year, entry-level contract with Minnesota in May, 2012.
2012-13: Gustafsson returned to Sweden for his second season with Lulea and was 20-13 with 4 shutouts in 33 SHL games. He had a 1.70 goals against and .932 save percentage for the fourth-place club. Lulea reached the finals against regular season champion Skelleftea. Gustafsson played 15 playoff games and was 8-7 with a 2.03 goals against and .925 save percentage.
Gustafsson is a solid technical keeper, with good size. He's still working on some of the finer points of his game, but reads the play well.
After another solid year with Lulea, Gustafsson is expected to compete with Darcy Kuemper for starts with Iowa in 2013-14.