2009-10: Patrick Sieloff played for the Compuware minor midget team in Michigan. In 37 games he scored 2 goals with 8 assists and had 52 penalty minutes.
2010-11: Sieloff joined the US National Team Development Program in Ann Arbor – appearing in one game for the U18 team and spending the bulk of the year with the U17 squad. Sieloff was scoreless with no penalties in his only game with the U18 team. In 52 U17 games he scored 3 goals with 6 assists and had 76 penalty minutes. He had 1 goal with 2 assists in four games as the USA finished first in the Four Nations Cup in November. In six games at the 2011 World Hockey Challenge he had 1 goal and 1 assist as the USA finished second to Canada Ontario. He skated in all three games as the USA won the 2011 Vlad Dzurilla U18 tournament in Slovakia. Sieloff committed to playing college hockey at Miami in 2012-13.
2011-12: Sieloff played for the NDTP U18 team and won a gold medal with the USA squad at the 2012 U18 World Junior Championship. In 60 games he scored 3 goals with 7 assists and had 113 penalty minutes. Sieloff was plus-three with no points or penalties in six games at the U18 WJC. He was invited to the NHL Draft Combine and was ranked 31st amongst North American skaters in Central Scouting's final rankings prior to the 2012 NHL Draft.
2012-13: Sieloff played 45 games for the Windsor Spitfires in his first OHL season before having to shut things down due to a hip injury in February. The 18-year-old skated for the gold medal-winning USA squad at the 2013 World Junior Championship in Ufa, Russia. He provided a physical presence on the Windsor blue line in his first season, scoring 3 goals with 8 assists and finishing -9 with 85 penalty minutes. The Spitfires finished fifth in the West Division. Sieloff had 1 assist and was an even plus/minus with 2 penalty minutes in six games at the WJC. The USA defeated Sweden, 3-1, in the gold medal game. Sieloff signed a three-year entry-level contract with Calgary in July, 2013.
Sieloff is tough, stay-at-home defenseman with a bit of offensive upside to his game. He is solidly built and isn't afraid to make use of his size or drop the gloves on occasion. But Sieloff is not just a goon as he is already a very good defender in his own zone and has the ability to at least get plays started from his own end of the ice. He is an effective penalty killer and has some leadership skills to go along with his grit.
Sieloff begins his pro career as a member of the Abbotsford Heat as the 2013-14 season commences. The defender is one of the new faces to the team and will have an opportunity to elevate his play to the next level. Sieloff will be watched closely after impressive summer camps to determine when he will be ready to make the leap to the NHL.