You can't just draw a line and say the rebuild started with the Shanahan regime. The turn around started with Shanny, but the players and assets Shanny used were earned over an 8 year stretch, not 2 years.
Quoting myself from another Leafs thread where people ignored everything pre-Shanahan
Leaf fans saying the rebuild started in 2015? What about 2008-2015? The leafs earned the right to pick top 5, 5 times in 8 years and top 10, 7 out of 8 years. Granted you traded away 2 of those picks, #2 and #9 for Kessel. Sabres didn't start picking top 10 until 2013, and only 2 top 5 picks, rather than 4 that the leafs ended up using. I'd say the Sabres are 3 years behind the Leafs, in terms of an 8 year rebuild.
2008 Luke Schenn #5 (from NYI, Toronto had the #7 pick) Turned into JVR
2009 Nazem Kadri #7
2010 Seguin #2 traded to Boston
2011 Dougie #9 also traded to Boston
2012 Morgan Rielly #5
2013 Gauthier #21
2014 Willy Nylander #8
2015 Marner #4
2016 Matthews #1