I kinda thought it was odd that after Niang made that shot to put us up 3, okie st called timeout, and Niang was still on the floor for defense, iirc it was the starting lineup out there.
I just figured take him out on defense by putting in either BDJ or Nader. If they miss, like they did, you know they're gunna foul, so you can get him back in, if they hit a two they have to foul, and if they do make the shot, Fred still has 3 timeouts.
What I think Fred is thinking is he trust Niang in that situation to play assignment defense. Knowing he's not gunna flat shut someone down, but at least he won't be outta position and give up a wide open shot. Other thing that's possible, is if they did drill a 3 there to tie, Fred doesn't want to call a timeout. He wants to bring it up as fast as possible, so the defense can't get set.