What do McGrady, Carter, Bosh, DeRozen and Ed Davis have in common?
They were all loans from American teams. They were at all points unlikely to resign with the Raptors. It is speculative for DeRozen and Ed Davis and would have been the same for Brandon Knight and Kemba Walker.
We spend 2 years giving them playing time while they are bad and we get them for 4 years where they play at an acceptable level. If they become great, we lose them.
By drafting or trading for players like Jonas Valanciunas, Tristan Thompson and Cory Joseph we can increase our chances of keeping them if they turn out to be great. Thus it is Valanciunas for the next 10-15(less, team choice, if he sucks) vs Knight for the next 6 years if he is good.
That is also not taking into account that Valanciunas is likely the best person to draft at the 5. Similar arguments could be applied to Biyombo, but he seemed really overblown given age concerns and I would be worried about his health long-term.
Also arguments about the team not getting immediately better are irrelevant. John Wall and Blake Griffin both led their teams to losing records.
I usually just read these forums but I believe many people are very wrong, prompting me to post.