2006-07: Grimshaw saw playing time for both the U-17 and U-18 squads in his first year with the US NTDP. In 32 games with he U-17 team, Grimshaw recorded five points (two goals, three assists) and spent 62 minutes in the penalty box. Grimshaw then joined the U-18 squad and played in 11 games, recording a goal and two assists.
2007-08: Grimshaw was a mainstay on the U-18 blue line, playing in 57 games. In his 57 games, Grimshaw scored two goals and added 10 assists. According to NHL Central Scouting’s final rankings, Grimshaw is the 205th overall North American skater for the 2008 NHL Entry Draft.
Grimshaw is a technically sound stay at home defenseman.