2009-10: Girgensons split his first season in North America between the Green Mountain Glades EJHL and Empire League teams and skated for Latvia at the 2010 U18 World Junior Championship. In 23 EJHL games he scored 11 goals with 17 assists and 13 penalty minutes. He had 2 assists in two playoff games. He was dominant in Empire League play as a 15-year-old, scoring 17 goals with 12 assists and 6 penalty minutes in 19 games. Girgensons scored 1 goal with 1 assist and was minus-1 with 2 penalty minutes in six games at the WJC. Latvia finished ninth in the ten-team tournament, avoiding relegation with a win over Austria. Girgensons committed to playing college hockey at the University of Vermont in 2012-13.
2010-11: Girgensons was the third-leading scorer for the expansion Dubuque Fighting Saints in the USHL and skated for Latvia in the 2011 U20 World Junior Division IA Championship. Girgensons scored 21 goals with 28 assists and was plus-seven with 46 penalty minutes in 56 games. Led by Flames prospect John Gaudreau, the first-year Fighting Saints finished first in the Western Division and won the Clark Cup playoff championship. Girgensons scored 4 goals with 3 assists and was +6 with 7 penalty minutes. Latvia was a perfect 5-0 in the tournament to gain elevation to the top division for 2011-12. Girgensons was selected by CSKA Moscow in the 2nd round (28th overall) of the KHL Draft and taken in the 1st round (45th overall) of the the CHL Import Draft by the Kelowna Rockets (WHL).
2011-12: Girgensons was the captain and leading scorer for Dubuque in his second season and was an assistant captain for Latvia in the 2012 U-20 World Junior Championship. Girgensons scored 24 goals with 31 assists and was plus-17 with 69 penalty minutes. Dubuque finished third in the East in the re-aligned USHL. Girgensons scored 2 goals with 2 assists in the playoffs – suffering a season-ending broken jaw in the second game of Dubuque's first round series with the US NDTP U17 team. He scored 2 goals and was minus-six with 6 penalty minutes in six games for Latvia at the WJC. Latvia avoided relegation with a 2-1 win over Denmark in its final game. Girgensons was ranked 18th amongst North American skaters in Central Scouting's final rankings prior to the 2012 NHL Draft. He signed a pro contract with the Buffalo Sabres following the team's development camp and will not be attending the University of Vermont.
A two-way player who is a tenacious forechecker with good speed, scouts rave more about Girgensons’ defense than offense. A hard worker without a standout skill, Girgensons projects to be a second-line center in the future and the perfect complement to Buffalo’s more offensively-oriented forwards.
Signing an entry-level contract means Girgensons will not be attending the University of Vermont. Because Girgensons has not played in the CHL yet, he is eligible to play in the AHL. If the Sabres think Girgensons still needs a little more seasoning playing against juniors, the Kelowna Rockets own his CHL rights.