I know Danny was really high on Winslow and was about to give up six picks (including 4 first-rounders) to get him. Most likely those picks were used to draft:
2015 Draft: Terry Rozier (No. 16), R.J. Hunter (No. 28) and Jordan Mickey (No. 33)
2016 Draft: Guerschon Yabusele (No. 16), Ante Zizic (No. 23) and Deyonta Davis (No. 31)
The Celts have cut Hunter, are soon to cut Mickey, have Euro-stashed Yabusel and Zizic, and trade the Deyonta Davis pick.
So right now would you trade Yabusele, Zizic, and Davis (or let's say the Memphis 2019 1st-rounder we got for him) in exchange for Winslow?
Winslow's numbers last season (in 18 games due to injury) were atrocious. They were Marcus Smart bad in terms of shooting percentage at .35/.20/.61. Yes, it was only 18 games, but that's still over 1/5th of the season.
http://www.espn.com/nba/player/_/id/3135047/justise-winslowHe averaged 10.9ppg in 34 minutes. While Jaylen Brown, who is the exact same height and weight, averaged 6.6ppg in 17 minutes with .45/.34/.68 shooting percentages.
http://www.espn.com/nba/player/stats/_/id/3917376/jaylen-brown