2007-08: Duncan Siemens was chosen in the first round, 3rd overall, of the 2008 WHL Bantam Draft by the Saskatoon Blades.
2008-09: Siemens played for the Sherwood Park Kings Midget AAA team, appearing in 34 games for that team. He scored 5 goals and added 13 assists for 18 points, while also chipping in with 68 penalty minutes. Siemens made his WHL debut with the Saskatoon Blades, playing in 2 games and recording 1 assist.
2009-10: Siemens played in his WHL rookie season with the Blades appearing in 57 games for that team. He scored 3 goals and added 17 assists for 20 points along with 8 penalty minutes. In 7 playoff games for the Blades, Siemens had no points and 11 penalty minutes. Siemens played for Team Pacific at the 2010 World Under-17 Hockey Challenge, picking up no points and 10 penalty minutes.
2010-11: In 72 games for the Blades, Siemens scored 5 goals and added 38 assists for 43 points. He also added 121 penalty minutes on the season. Siemens played for Team Cherry at the 2011 CHL Home Hardware Top Prospects Game.
2011-12: Siemens made his pro debut as an 18-year-old – playing in three late season games with Colorado's AHL affiliate Lake Erie following his third season with Saskatoon. He was scoreless and minus-one with 2 penalty minutes during his time with the Monsters. Playing on the top pairing for Saskatoon along with Montreal prospect Dalton Thrower, Siemens scored 6 goals with 22 assists and was plus-12 with 91 penalty minutes in 57 games. The Blades finished third in the East Division. Siemens had 1 goal and 1 assist and was minus-two with 10 penalty minutes in the four-game playoff series with Kamloops.
2012-13: Siemens experienced extreme highs and lows in his fourth WHL season with Saskatoon. Expected to be the team captain, that role instead went to 20-year-old Brenden Walker. After getting off to a slow start, the Blades turned things around and Siemens was a big part of that. In 70 regular season games he scored 3 goals with 29 assists and was +31 with 109 penalty minutes. Saskatoon finished first in the East Division but was swept by Medicine Hat in a first round playoff series. Siemens had 1 assist and was +1 with 2 penalty minutes in the series. The Blades hosted the 2013 Memorial Cup and pulled off a shocker – defeating eventual champion Halifax – but were also the first team to be eliminated. In four Memorial Cup games Siemens had 1 assist and 8 penalty minutes.
A physical, in-your-face defender with size and an underrated offensive game, Siemens is the complete package. Capable of playing half of the game, Siemens is comfortable playing at both ends of the ice and in any situation, be it even-strength, with the man advantage or on the penalty kill.
As one of the youngest draft eligible players of the 2011 draft class, Siemens still has lots of room to develop and his ceiling is difficult to determine. He will likely spend another couple years in the WHL getting stronger before competing for regular NHL duty. He projects as a top pairing defenseman at the pro level.