Andrew Nielsen was drafted by the Leafs last year 65th overall and has just finished his season with the Lethbridge Hurricanes of the WHL. He is listed at 6'3" and 207 lbs.
He ended up 8th in primary points in the WHL amongst defencemen with 18 goals and 18 assists, good for 11th in primary poinst per game played for defencemen.
For more detail, check out this statistical look at him or Scott Wheeler's most recent review of the top 25 under 25, where he had this assessment:
Despite an excellent (surprisingly so) season from Andrew Nielsen, he remained unranked. Like with Dermott, I worry about how Nielsen's skating will translate as a pro (his shot and physicality aren't a problem). Still, his season has been extremely impressive and he doesn't seem to be slowing down as the WHL's highest-scoring defensemen.
Chase Witala was also signed today. He is an undrafted junior left-wing/centre with his home town team, the Prince George Cougars. He is listed at 6' and 170 lbs, and led his team in scoring with 40 goals and 39 assists and is 23rd in the WHL in primary points per game at 20 years old.
Witala attended a propect camp last year for the Dallas Stars, so he has some experience outside junior hockey.
Some stats are from Prospect-Stats